priciples of insecticide use in rice ipm

DRR Technical Bulletin 30/2008 

Correct citation : 

N.V. Krishnaiah, V. Jhansi Lakshmi, I.C. Pasalu, G.R. Katti and Ch. Padmavathi, INSECTICIDES IN RICE 

IPM PAST, PRESENT AND FUTURE. Technical Bulletin No.30, Directorate of Rice Research, Hyderabad, 

A.P. India – pp : 146 

Published by : 

Dr. B.C.Viraktamath 

Project Director 

Directorate of Rice Research 

RajendraNagar, Hyderabad- 500 030, India 

Tel : +91 -40-24015120,2401 5026-39 

Fax : +91-40-2401 5308 

Website : www.drricar.org 

Email : pdrice@drricar.org 

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FOREWORD 

Rice, the staple food of more than half of human population is grown in 153.9 million hectares in the 

world with a production of 618million tones and a productivity of 4.02 tones /ha. 

India ranks first in the world in rice area with 44.3 million hectares. But our productivity is only 3.01 

t/ha, which is below world average. Insect pests, diseases and weeds cause considerable are the 

major deterrents in enhancing rice productivity in the country. Among these, insect pests alone cause 

about 10% loss in yield. To avert the damage by these insect pests, farmers are forced to apply 

insecticides. 

There is vast information generated on the effectiveness of insecticides, methods of application and 

associated problems like insecticide resistance, pest resurgence, secondary pest outbreaks, effects 

on non-target organisms etc. in all the major rice growing countries during the last 40 to 45 years of 

post green revolution era. Entomologists at our Directorate have made untiring efforts in gathering 

almost the vast information on insecticide usage in rice with special emphasis on insecticides as a 

component of IPM. 

The information has been arranged thematically and presented in an easy and readable way. This 

should serve as a source of the past and present knowledge of insecticide utilization in rice. This 

should also serve as a ready reckoner with the most updated information on all aspects of insecticides 

for the researchers, students, agrochemical agencies and those engaged in insecticide production 

and evaluation in rice. 

(B.C. Viraktamath) 

Project Director

PREFACE 

Insect pests, in general, damage crops resulting in an yield loss of about 10%. In case of rice also, 

insect pests cause about 10 to 15% reduction in yield as evidenced by multi-location experiments 

conducted under AICRIP for the last 40 years. To avert these losses, integrated pest management 

(IPM) is adopted as a national policy in India. In IPM, the major emphasis in rice is given for development 

of varieties resistant to insect pests. However, there are no sources of good level of resistance, even 

to major insect pests like stem borer and leaf folder. For brown planthopper and whitebacked 

planthopper, the level of host plant resistance is only moderate. Good level of resistance is available 

for gall midge, but the problem of biotypes is crippling the release of resistant varieties suitable for 

all areas. Pheromones have come to a stage of practical exploitation only in case of stem borer. The 

cultural methods like optimum fertilizer application, clean cultivation etc. are being followed as in 

other crops. In the given scenario, insecticide application to protect rice crop is becoming a necessary 

evil, which is forcing rice entomologists to continue research to fully exploit the potential of this 

component of IPM. 

For quite some time, there were misunderstandings about the role of insecticides in rice IPM. Some 

entomologists argued that IPM means completely avoiding insecticide usage, but, the practical field 

situation under farmers’ conditions is entirely different. Rice farmer has to resort to use of susceptible 

varieties for their own obvious reasons and are forced to apply insecticides whenever some pest 

problems arise. 

Unfortunately, international organizations have discontinued the insecticide evaluation programmes 

in rice. Hence, national programs like AICRIP have to shoulder the responsibility of generating the 

information on the effectiveness of new molecules of insecticides against all the major and minor 

insect pests of rice. This has been effectively executed under AICRIP for the last forty years. Therefore, 

it is apt to review the whole scenario of insecticide evaluation program under AICRIP along with 

related efforts by entomologists from other rice growing countries like China, Japan, Korea, Philippines, 

Sri Lanka, Indonesia and Malaysia. 

There is no comprehensive source of information available on the effectiveness of insecticides against 

major insect pests. Hence, we the entomologists at DRR made an attempt in our own humble way to 

collect, organize and thematically present the whole information on various aspects of insecticide use 

in rice IPM, its past, current status and future directions. 

N.V. Krishnaiah, V. Jhansi Lakshmi, I.C. Pasalu, 

G.R.Katti, Ch.Padmavathi

CONTENTS 

Integrated Pest Management in Rice 1 

Bio-ecology of major rice pests 6 

Insecticides used in rice IPM 16 

Principles of insecticide use in rice IPM 21 

Effectiveness of insecticides against rice insect pests 31 

Methods and timing of insecticide application in rice 43 

Systemic nature of insecticides in rice: the concept and practice 50 

Molecular approaches for insecticide utilization in rice 54 

Safety of insecticides to natural enemies in rice ecosystem 59 

Insecticide resistance in rice pests 67 

Insecticide induced resurgence in rice pests 79 

Botanical insecticides in rice pest management 89 

Biopesticides and their use in rice IPM 101 

Management of green leafhopper, the vector of rice tungro disease with insecticides 104 

Future strategies 109 

References 112 

Acknowledgements 146

Introduction 

Insecticides in Rice IPM (DRR) 

INTEGRATED PEST MANAGEMENT IN RICE 

Rice is grown mainly in Asian countries like China, India, Japan, Korea Republic, Srilanka, Pakistan, 

Bangladesh, Indonesia, Malaysia, The Philippines, Thailand etc. More than 90% of rice is produced and 

consumed in these Asian countries. Rice is biologically, ethologically and culturally bound with the life of 

Asians. The total rice growing area in the world is 153.9 million hectares with a production of 618 million 

tons of rough rice. Among the rice producing countries, India occupies number one position with regard 

to area with 44.3 million hectares followed by China (29.3 million ha.). However, with regard to the 

productivity or per hectare yield of rice, India occupies 15th or still lower position with 3.01 t./ha of rough 

rice, compared to China (6.26t./ha.), Japan (6.65t./ha.), Korea Republic (6.57t./ha.), Indonesia (4.57t./ 

ha.), Malaysia (3.36t./ha.),The Philippines(3.65t/ha.), SriLanka(3.51t./ha.)etc.(FAO,2006). The major 

reasons for low productivity in India are the losses due to insect pests, diseases and weeds. Insect pests 

alone are responsible for 10-25% yield losses in India. 

There are several methods like host plant resistance, cultural measures, optimum time of sowing and 

transplanting, recommended and balanced fertilizer application, water management, biological control 

methods like conservation and utilization of parasitoids and predators, biorational methods like use of 

insect pheromones, botanicals and need based insecticide use. Utilization of as many techniques as 

possible into a unified programme is called integrated pest management or IPM. This has been accepted 

and attempted as a national policy in India. 

There are over a dozen definitions propounded by various authors for the concept of integrated pest 

management (IPM). However, the salient points of all the definitions are that 

(1) IPM is an ecosystem approach in pest management in which all the natural 

forces of pest suppression are strengthened. 

2) One or more methods of pest suppression are employed into a unified command. 

3) The option(s) of least possible disturbance in the agri-ecosystem like rice ecosystem is (are) 

employed. 

4) With the awareness of the limitations imposed by the fact that agro-ecosystems are “artificial 

ecosystems”. 

Philosophy of IPM 

The insects have come into existence during the course of evolution about 300 million years ago, while 

man appeared on the scene of evolution only about one lakh years ago or even later. The insects have 

invaded all spheres of earth both terrestrial and aquatic. They adapted to all types of food materials 

available on the planet. They developed physiological mechanisms to cope up with any adverse conditions 

1


in terms of biotic and abiotic factors. Above all, the insects have immense reproductive potential. The 

insect pests of crops in general and rice in particular developed high physiological abilities of adaptation. 

For instance, the fact that there are no sources of host plant resistance to many rice insect pests like stem 

borers, leaf folders, rice hispa, gundhi bug etc. is an expression of their high level of adaptation to rice 

plant. As rice is grown in different ecosystems, like irrigated, deep water, upland and rain-fed lowland, the 

adaptation of different pests is fine-tuned to suit that particular ecosystem. Termites and root aphids are 

present in uplands only, while gall midge is confined mainly to irrigated rice ecosystem. 

The major philosophy of IPM is to live with the insect pests instead of attempting to completely eliminate 

them from rice ecosystem. At the same time the farmer has to safe guard the yield levels of the crop. 

Hence, he can tolerate only up to certain level of pest population or damage. Hence, the concept of 

economic thresholds (ETLs) was arrived at. 

Concept of ecosystem 

“Ecosystem in general is any unit having living organisms and non-living environment representative of 

an area with effective interaction between the living organisms and the non-living environment, leading to 

trophic levels, material cycles and energy flow” (Odum, 1971). 

In a natural ecosystem like a forest, the vegetation serving as the energy source for all the animal 

kingdom is permanent, evolved over millions of years ago, consisting of many plant species and best 

suited to the climate. The phytophagous animals including insects feeding on these plants never increase 

beyond certain levels as the natural enemies like parasitoids and predators automatically push down the 

phytophagous insect populations. All this is possible because the vegetation in forest ecosystem is 

permanent and stable. 

If we compare now the rice crop as an ecosystem with the forest we can clearly understand the differences. 

Here a single species that too a single variety of rice is fed with nutrients of NPK, Zn etc to serve as a 

feast for phytophagous insects and boost their populations. The natural enemies will try to push down the 

phytophagous insects but cannot cope up with the tremendous reproductive abilities of phytophagous 

insects. Hence, natural enemies are present only as passive dependants on phytophagous insects and 

cannot actively push down their populations. Further, once the crop is harvested, the natural enemies are 

destroyed and hence they have to re-colonize and start multiplying on the phytophagous insects all 

afresh. Thus, it is clear why natural biological control alone is not sufficient to push down pest levels in rice 

ecosystem. 

Thus in rice IPM, the farmer needs to depend on other methods like host-plant resistance where ever 

possible, sow and plant in time, monitor the pest populations so that they do not cross ETLs, adopt 

cultural methods like optimum and recommended fertilizer levels, proper water management, adoption of 

pheromones, botanicals, biopesticides or other non-pesticidal approaches along with need based application 

of insecticides. 

2


Pit-falls lie in understanding the concept of IPM 

The difficulties lie in understanding how the concept of IPM has been evolved. It was thought that the 

agro-ecosystems like rice need no pesticide application at all or integrated pest management means / or 

synonymous with concept of ban on use of pesticides in rice ecosystems. Therefore, it was stated that 

agro ecosystems like rice crop needs only to be planted and left to Mother Nature for its care during the 

rest of the cropping period. Our past experience proves to the contrary. In many of the experiments, it 

was observed that even under normal cultural practices with recommended fertilizer levels normal irrigated 

rice crop suffers very heavily from insect pests like stem borer, gall midge, brown planthopper, whitebacked 

planthopper and leaf folder etc. The loss can be between 10 to 25%. 

Fertilizer application Versus the Concept of IPM 

Usually, rice farmers in deltaic areas apply more than the recommended doses of fertilizers, particularly 

‘N’. It is this tendency that encourages pest build-up and leads to more pest problems. This practice is 

responsible for further enhancing the magnitude of major pests and minor and sporadic pests attaining 

major pest status. Therefore, farmers must be advised to strictly follow fertilizer levels based on local 

recommendations which depend on the variety, soil type, water management etc. It is collectively called as 

“good agronomic practice (GAP). This should form the base and a part of IPM. 

Host Plant Resistance versus IPM 

Integrated pest management is a practical approach in which utilization of pest resistant varieties is the 

key component. But the major limitation in full utilization of host plant resistance for pest management is 

lack of suitable resistant sources to major insect pests like stem borer and leaf folder in rice. Good 

sources of resistance are available in case of gall midge, but development of biotypes is a limitation. But 

still gall midge resistant varieties are extensively cultivated in many endemic areas, which need no chemical 

protection. In case of brown planthopper and whitebacked planthopper, the resistance sources are moderate 

and also not being fully exploited. At farmers’ level, the major considerations in selecting a variety are its 

high yield, grain quality, price of the produce and availability of market to that particular variety in the 

region. Host plant resistance at least to major insect pests of the region in a variety is only a secondary 

consideration for the farmer. For instance farmers in Krishna Godavari Zone of Andhra Pradesh and 

Tungabhadra Delta of Karnataka are growing only BPT 5204 and Swarna in majority of the area although 

these are susceptible to the major insect pest like brown planthopper in these deltas. Similarly, in Kerala 

red kernel varieties are preferred over white kernel varieties and it is the red kernel varieties that fetch 

premium price to the Kerala farmers in the market. Hence, Kerala farmer goes only for red kernel varieties 

whether they are resistant or susceptible to brown planthopper, the major menace in the state. However, 

there are many brown planthopper resistant varieties with white kernel but these did not find acceptance 

with the Kerala farmers. 

3


Biological control versus IPM 

There are many species of parasitoids and predators for all the major insect pests of rice like stem 

borers, planthoppers, leafhoppers, and gall midge etc. Many species of spiders present in rice ecosystem 

also prey on these major insect pests. Even when rice is sown and planted normally and fertilizer application 

is at recommended dose, there are instances of 10-25% infestation of rice crop by stem borer and gall 

midge in endemic areas if the crop is unprotected (DRR, 2006). There are several occasions where 

hopper burn has occurred due to planthoppers if timely intervention with insecticide application is not 

resorted to. Any number of examples like this can be cited. The basic question is if the natural biological 

control existing in rice ecosystem is sufficient to keep the insect populations below economic threshold 

levels, the occasions described above should not have occurred. This means that human intervention 

through use of insecticides is an unavoidable evil to protect rice crop from insect pests. 

Integrated pest management does not involve only insect pests 

IPM involves diseases, weeds, rodents, other invertebrate pests like snails etc. Farmer at his level has to 

confront with all these problems in adopting the strategy of integrated pest management. The scientists 

in different disciplines plan and execute the incorporation of resistance in the varieties concerning their 

own disciplines. For instance in Punjab, Haryana and Western Uttar Pradesh bacterial leaf blight is a major 

menace. Other problems are pink stem borer, yellow stem borer, whitebacked planthopper and leaf folder. 

When the whole situation is taken into consideration there are no varieties with good level of resistance to 

these insect pests. On the other hand, varieties resistant to bacterial leaf blight are available. Another 

consideration is that these insect pests can be managed by utilizing suitable insecticides or other materials. 

But there are no effective chemicals so far identified against bacterial leaf blight. Therefore, farmers of 

Punjab have to choose necessarily the varieties with bacterial leaf blight resistance. In coastal Andhra 

Pradesh and delta areas of Karnataka, along with brown planthopper and whitebacked planthopper, 

sheath blight is a major menace. But there are no sources of resistance to sheath blight in the entire rice 

germplasm evaluated so far. The brown planthopper resistant varieties released in these areas were 

found acceptance with the farmers for some time. But later they have shifted to the susceptible varieties. 

Therefore, farmers in this area have to manage both brown planthopper and sheath blight together. 

Economic thresholds and economic injury levels in adoption of IPM 

As per the definition “Economic threshold levels are the levels of pest population / infestation at which 

control measures have to be initiated so that the pest population or damage will not reach the economic 

injury level”. Economic injury levels have been defined as the levels of pest populations / damage where 

the loss in economic yield equals to the cost of crop protection or cost of management options. 

There are certain lacunae in understanding the concept of ETLs in pests and diseases on the part of 

many plant protection scientists as well as farmers. ETLs are only broad guidelines in taking up control 

measures against the pest or pests or diseases in a given area and given situation. For instance, in brown 

4

The following are the Economic Threshold Levels for major insect pests 

Insect pest Economic thresholds 


Brown planthopper/ 10 insects per hill at vegetative stage or 20 insects per at later 

whitebacked planthopper stages 

Stem borer 5-10% dead hearts or 1 egg mass / sq m or 1 adult moth / sq. m. 

Leaf folder 3 freshly damaged leaves / hill at post active tillering stage 

Green leafhopper 2 insects / hill in tungro endemic areas. 20-30 insects /hill in other 

areas. 

Gundhi bug 1 nymph or adult / hill 

Gall midge 5% silver shoots at the active tillering stage 

planthopper endemic areas where whitebacked planthopper is also present the population of both the 

planthoppers is to be taken into consideration while deciding 15 to 20 insects / hill as ETL. In these areas 

if the leaf folder is also a major menace, even if the intensity of all the pests is below economic threshold 

in respect of individual pests as cited above, the control measures have to be initiated early. Similarly, in 

areas where brown planthopper and whitebacked planthopper are problems, sheath blight is also a major 

menace, the level of damage by sheath blight is also to be considered while initiating necessary management 

practices. 

Another important consideration while deciding the ETL is the stage of the plant. Usually, for the incidence 

of yellow stem borer in vegetative stage, 5% dead hearts is considered as ETL. However, at heading 

stage, there is no level of white ear heads fixed as ETL because the damage at this stage is not compensated. 

Hence, as per the guide lines one moth or 1 egg mass per sq. m. during flowering phase or even slightly 

earlier has to be considered as ETL. Further, to prevent the white ear head damage, the management 

measures have to be initiated before panicle emergence itself. Similarly, in case of neck blast infestation 

also, more or less similar guidelines have to be followed. 

5


BIO-ECOLOGY OF MAJOR INSECT PESTS OF RICE 

Rice is cultivated in varied environments like uplands, deep-water, shallow-low lands and irrigated conditions. 

However, the most preferred ecology of the rice plant is tropical and humid climate with a temperature 

range of 15-35 0 C and RH of 85-100%. This climate is also best suited for the survival and multiplication 

of many insects. Therefore, a large number of insects got adapted for feeding on rice and utilize it as their 

food. There are more than 100 insect species recorded as feeding on rice plant. About 20-25 of them 

reached the status of pests causing economic losses under farmers’ field situations. Among them, stem 

borers, planthoppers, leafhoppers, leaf folders, gall midge, rice hispa, gundi bug, case worm, army 

worm, cut worm, mealy bugs and rice thrips are the most important in India and other countries. A brief 

bio-ecology of these pests is presented below. 

Stem borers 

The stem borers attack rice crop throughout the growth period from nursery up to harvest. The damage 

results in characteristic symptoms of ‘dead hearts’ or ‘white ears’ depending on the stage of the crop. 

During vegetative phase, the stem borer larvae emerge from the egg masses laid on leaves and enter the 

tiller to feed inside, resulting in the characteristic damage of ‘dead heart’. In the damaged plants, the 

central leaf whorl does not unfold, turns brownish and dries out although the lower leaves remain green 

and healthy. The affected tillers do not grow further and eventually dry. The dead heart comes out easily 

6 

YSB Male YSBFemale YSB Egg mass 

YSB Pupa 

YSB Larva


when pulled and emits foul smell. At reproductive stage, the damage is characterized by whitish, erect 

and chaffy panicles, which are very conspicuous in field and are called ‘white ears’. However, the stem 

borer damage may occur during the grain filling stage also, leading to stoppage of further grain filling and 

resulting partially filled grains. 

There are five species of stem borers distributed throughout India. Among these, yellow stem borer (YSB), 

Scirpophaga incertulas (Walker) is the most important, widespread, dominant and destructive. The other 

borers are, pink stem borer, Sesamia inferens (Walker) occurring mostly in rice-wheat cropping systems 

of north-west, white borer, Scirpophaga innotata (Walker) common in southern region particularly in 

Kerala, dark headed stem borer, Chilo polychrysus (Meyrick) and striped stem borer, Chilo suppressalis 

(Meyrick) in states of West Bengal and Assam respectively. 

In southern parts of India where rice is cultivated through out the year, there are usually 3 generations 

during kharif season and 2 generations during rabi season. Similar is the case in most parts of eastern 

states like Orissa, West Bengal and the north eastern states like Assam, etc. However, in north western 

parts of India, where one crop season of rice is prevailing, the yellow stem borer completes 2-3 generations 

during kharif and enters into quiescent stage or diapause in larval stage during October-November 

immediately after rice is harvested. It remains in that stage through out the winter months of December to 

February-March. With rise in the temperatures during March, the diapause is broken, the larva pupates 

and emerges as adult from April beginning on wards. 

Brown planthopper, Nilaparvata lugens (Stal.) 

Brown planthopper emerged as a major pest of rice in India only after 1972, when large scale adoption of 

short-statured high yielding and high nitrogen responsive varieties occupied major areas in deltas of A.P., 

BPH Adults BPH Eggs 

BPH Nymphs BPH Damage 

7


Tamil Nadu, Kerala and Karnataka, although this pest was notorious in parts of China, Japan, North and 

South Koreas even during early parts of 20 th century. In those countries japonicas were traditionally 

grown with high fertilizer levels. The microclimate of rice crop which existed in japonica varieties in those 

countries also started prevailing in India, Philippines, Indonesia etc. which are tropical countries, after 

large scale adoption of dwarf varieties. Although the microclimate in these tropical countries is not precisely 

delineated, shady atmosphere, high humidity, improper aeration, coupled with optimum temperature of 

25-30 0 C appear to be responsible for rapid build up of BPH causing heavy losses. Heavy nitrogen 

application associated with dwarf varieties also appeared to be responsible for major BPH epidemics in 

tropical countries. 

Adult BPH are dimorphic. Winged as well as half winged males and females along with nymphs occur as 

mixed populations in fields. Both adults and nymphs suck sap from the base of the tillers, resulting in 

yellowing and drying of the plants. At early stages of attack, round yellowish patches appear which soon 

turn brownish due to drying up of the plants. The patches of infestation spread in concentric circles within 

the field and in severe cases the affected field gives a burnt appearance known as ‘hopper burn’. The 

hopper populations can multiply very fast and migrate over long distances causing widespread infestation 

in short time. Apart from causing direct damage, BPH also acts as a vector of grassy stunt virus. 

The life cycle of the insect is completed within 20-25 days depending on temperature. There are usually 

3-4 overlapping generations during the crop season. The winged adults settle in the crop after 15-20 

days of transplanting. But the population will be very low. It is of the order of 2-5 insects per 100 hills. 

Hence, farmer cannot recognize its presence. It is only during 3rd or 4th generation we can see the 

population in damaging proportions. By that time, the crop comes to flowering phase. That is the reason 

why farmers think that BPH attacks rice crop only at flowering phase (Krishnaiah et al., 2006b). 

Whitebacked planthopper, Sogatella furcifera (Horvath) 

During 70s and 80s whitebacked planthopper (WBPH) used to be confined to north-western belt of 

Punjab, Haryana, and western Uttar Pradesh. Later, the pest has spread to almost all areas where rice is 

grown and started occurring together with BPH in many deltas of the southern states. This has emerged 

as a serious pest in areas particularly where rice varieties resistant to BPH are grown. The partially 

8 

WBPH Adults WBPH Eggs WBPH Nymphs


cleared ecological- niche due to low population of BPH on resistant varieties appeared to have triggered 

the multiplication of WBPH on those varieties. 

WBPH is relatively smaller in size compared to BPH with a conspicuous white spot on dorsal thorax. Hence, the 

name whitebacked planthopper. The nature of damage and the biology of WBPH are similar to BPH. Both 

nymphs and adults suck the plant sap from phloem and cause drying up of plants. Unlike BPH, it does not cause 

sudden and severe hopper burn. WBPH is not known to transmit any of the virus diseases of rice. 

The ecological conditions like high humidity (90 to 100%), optimum temperature (22 – 27oC) is very similar to 

BPH. The most significant difference between BPH and WBPH is that WBPH tends to be more numerous during 

early stages of crop growth i.e. up to 40 DAT, while BPH multiplies faster later on. In many of the deltaic areas 

WBPH is confined mostly to kharif season while BPH occurs during both kharif and rabi seasons. 

Green leafhoppers Nephotettix virescens (Distant) and Nephotettix nigropictus (Stal) 

There are two species of green leafhopper occurring in rice viz., Nephotettix virescens (Distant) and Nephotettix 

nigropictus (Stal). Both the leafhoppers suck the sap from rice plant from phloem as well as xylem. But unlike 

planthoppers, green leafhoppers do not cause hopper burn. These two insects are economically important as 

vectors of rice tungro disease (RTD). They transmit RTD from one plant to another and act as vectors of the 

GLH Adults GLH Eggs GLH Nymphs 

disease. Rice is the main host for N. virescens although it can feed on some grassy weeds occurring on rice 

bunds. N. nigropictus feeds mainly on Leersia hexandra and other weed hosts and occasionally feeds on rice 

crop. RTD is transmitted from weed hosts to rice crop mainly through N. nigropictus while the transmission 

among the rice plants is mainly by N. virescens. GLH lay their eggs either in the mid rib of leaves or in leaf sheath. 

The nymphs of N. nigropictus are brownish to pinkish in colour while the nymphs of N. virescens are light green 

in colour. N. nigropictus has a conspicuous black spot on the head, which is absent in case of N. virescens. 

The optimum conditions for multiplication of N. virescens and N. nigropictus are about 25 o C temperature and 

80% RH. Both the insects are more numerous during September and October months of kharif. Another GLH 

species called N. cinticeps (Uhler) is present in Japan and Korea and it is not prevalent in India. 

9


Gundhi bugs Leptocorisa acuta (Thunberg) and Leptocorisa oratorius (Fabricius) 

There are mainly two species of gundhi bug viz., Leptocorisa acuta (Thunberg) and 

Leptocorisa oratorius. The nymphs as well as adults emit a characteristic offensive 

odour in infested fields, which can be very easily recognized as a signal of presence 

of gundhi bug in rice fields. The nymphs and adults feed on developing milky grains 

causing brown spots and results in damaging the quality of the grain. At times, it 

becomes more serious and can cause heavy losses. The eggs are laid in rows on 

upper or lower side of leaves. There are five nymphal instars, which last for 25 to 30 

days. 

Leaf folder Cnaphalocrocis medinalis (Guenee) 

There are six to eight species of leaf folders attacking rice crop but the most important one is Cnaphalocrocis 

medinalis (Guenee). As the very name indicates the larvae, after emerging from eggs, fold the leaves with the 

10 

LF Female LF Male LF Eggs 

LF Larva LF Damage 

Gundhi Bug Adult 

help of silken threads secreted from salivary glands, remain inside and feed on the chlorophyll content of the 

leaves leaving only the lower epidermis. As a result, the photosynthetic activity is affected resulting in loss of 

grain yield. The loss in yield is more significant when larvae feed on boot-leaf compared to other lower leaves. 

There are 5 larval instars, which are completed in 18 to 25 days depending on the temperatures. The pupation


occurs inside the folded leaf, and the pupal period lasts for 5 to 7 days. The adult emerges and after mating 

starts laying eggs singly or in groups of 2-3 either on the lower side or upper side of the leaf or sometimes on 

leaf sheath. The egg period lasts for 4-6 days. The population of leaf folder, increases tremendously at higher 

nitrogen levels. As farmer tends to apply more than recommended nitrogen, leaf folder is becoming more 

serious in many of the irrigated rice growing deltaic tracts in many states. Of late, the population of leaf folder 

is increasing in plots treated with either phorate or carbofuran granules. 

Gall midge Orseolia oryzae (Wood Mason) 

The maggot of rice gall midge enters inside the young rice plant and starts feeding on growing portions. As a 

result, the meristematic tissue grows and encloses the feeding insect inside. The meristematic tissue as it grows, 

turns into a pale green tubular structure called “silver shoot.” The larvae pupates inside the silver shoot and 

emerges as adult from the top portion of silver shoot. The damaged tiller does not bear panicle. The crop under 

severe infestation is stunted with more numerous tillers. These new tillers are also eventually attacked resulting 

in almost 80 to 90% loss under severe infestation conditions. 

GM Adult GM Eggs GM Larva 

GM Pupa GM Damage 

The damage is more serious during kharif or wet season, although, gall midge started infesting rabi rice also in 

some of the coastal rice growing tracts. For proper egg hatching of gall midge, 90 to 100% humidity is 

essential. High humidity and a thin film of water are required for larval dispersal and entry into the plant. The 

female adult is a mosquito like dipteran fly with reddish abdomen. The male is slightly smaller in size with 

11


brownish abdomen. The adult life span is one to four days. The mating occurs immediately after emergence and 

eggs are laid any where on the foliage. The eggs are microscopic, cigar shaped and the egg period is about 

three to four days. There are five larval instars, which last for twelve to fifteen days. The optimum temperature 

for rice gall midge is 22 to 26 oC. Gall midge is more severe, in late planted conditions. 

Although a number of gall midge resistant varieties are released, their spread is hampered due to the 

problem of biotypes. 

Rice hispa Dicladispa armigera Olivier 

The adults of rice hispa (Dicladispa armigera Olivier) are shining black beetles 

with spines on forewings. Both adults and grubs damage the crop. The adults 

scrap the chlorophyll content on the upper side and lower side of leaves. The 

grubs mine in between two epidermal layers and feed on the chlorophyll content. 

In severe infestations, the crop gets dried with whitish appearance without any 

green colour. In cases of epidemics, about 25- 50 beetles may be present on a 

single hill. This pest is more serious in young stages of the crop growth either in 

nursery or in early transplanted conditions. 

Hispa Adult 

The adult beetles lay eggs singly either on the lower surface or on the upper surface of leaves covered 

with a brownish material. The egg period is about six to seven days. The emerging grubs directly enter 

between the two epidermal layers and grow there. The total larval period (five instars) lasts for 15 –18 

days. The pupation occurs in the larval mine in between the two epidermal layers and the pupal period 

lasts for 4 to 5 days. 

Hispa used to be a sporadic pest previously. However, it is occurring regularly in many Sub-Himalayan 

areas and also in north-eastern states. 

Case worm Adult 

12 

Case worm Nymphula depunctalis (Guenee) 

Case worm Nymphula depunctalis (Guenee) is a sporadic pest and occurs usually 

in young crop located in stagnant water. The attack is usually patchy and not 

continuous. The larva cuts the leaves into small bits and makes them into cases 

of approximately its own body size.The larvae remain inside the case and feeds 

on leaves, by scrapping the chlorophyll content. As a result, the plant growth 

and vigour are seriously affected. If the leaves are disturbed, the cases along 

with larvae fall on water surface. This is the characteristic symptom of case 

worm attack. The larva is aquatic and can breathe with gills.


Cut worms Mythimna separata (Walker) and army worms Spodoptera mauritia (Boisd.) 

These are a group of noctuid pests occurring sporadically in rice. The most 

important among these insects are (1) the army worm Spodoptera mauritia 

and the cut worm Mythimna separata. The former is a gregarious pest. It 

used to cause severe losses to rice crop before the green revolution era. 

This pest moves from one field to another field in large numbers like an army 

Cut worm Larva 

and almost completely defoliates the rice crop in the fields they invade. Hence, 

the name army worm. Cut worms, at times become serious and feed on the foliage during initial stages of 

crop growth. After flowering, the larvae climb and cut the ear-heads resulting in falling of the entire ear 

head or a part of the ear-head. This results in very serious losses to the crop. The infestation may occur 

just before harvest leading to falling of even matured grains in huge quantities. 

Mealy bug Brevennia rehi (Lindinger) 

Mealy bug damage & adult (inset) 

Rice thrips Stenchaetothrips biformis (Bagnall) 

Mealy bug is a common pest in upland and dry areas and in fields with 

uneven surface and where plant stand is not uniform and patchy. 

These mealy bugs are covered by a distinct waxy and powdery coating. 

Ants frequently visit the mealy bug infested plants and help in the 

dispersal of bugs from one plant to another. Both the adults and 

nymphs suck the plant sap resulting in the stunted growth and curved 

yellowish leaves. In severe infestations, plants dry up and panicles do 

not emerge from the boot leaf. Damage occurs in patches and is 

severe under moisture stress conditions. 

Rice thrips (S. biformis) occur during the seedling stage and in early transplanted crop. The nymphs and 

adults suck the sap from the leaves. Due to this feeding, initially yellow streaks appear on the leaves and 

Thrips Thrips Damage 

13


later they curl longitudinally from the margins inwards. These have sharp pointed leaf tips resembling 

needles, which finally dry up. The plants become lanky and present a sick appearance. 

Black bug Scotinophara sp. 

Black bug or Malayan bug is a common name for a group of Pentatomids belonging to the genus 

Scotinophara. Three species namely, S. coarctata (Fabricius), S. lurida (Burmeister) and S. bispinosa 

(Fabricius) were found in India. Both nymphs and adults suck sap from the base of rice stems and infest 

rice plants from seedling to flowering stage. Adults are black in colour and can live up to seven months. 

Female lays about 200 eggs at the basal portion of the rice plant near the water surface. Freshly laid 

eggs are green in clour and turn pink before hatching. Egg period lasts for about 4-7 days. Nymphs are 

light brown with yellowish green abdomen. They pass through four to five instars in about 25- 30 days. 

The bugs aestivates in cracks of bunds in the adult or late nymphal stage. 

Leaf mite Oligonychus oryzae (Hirst) 

Leaf mites feed on upper and lower surface of rice leaves. Usually they are more numerous on lower 

surface than upper surface. Leaf mites are small and microscopic spider mites which pierce the leaf 

tissue and suck the exuding sap. They multiply very fast under congenial condition and damage the entire 

14 

Mites Mite damage 

leaf portion under severe infestation. The damage results in the appearance of yellowish brown specks 

which increase under severe conditions and whole leaf turns to brown with complete loss of chlorophyll. 

The secretions of leaf mites form minute webs on the damaged surface of the leaf. These complete life 

cycle in 10-12 days. 

The damage is most serious during summer months when the temperature is high and humidity is low 

compared to winter and rainy seasons. 

Panicle mite Steneotarsonemus spinkii Smiley 

Sheath mite or panicle mite is transparent, microscopic tarsonemid mite which is mostly confined to 

internal tissues. Sheath mite attacks rice at panicle initiation stage and confines to the area between leaf


sheath and the stem. With the development of panicle inside the boot, sheath mite moves to the panicle 

and starts damaging the internal tissues of developing grains. As a result the grains become sterile and 

ill-filled. In association with the sheath rot fungus, Acrocylindrium oryzae, sheath mite or panicle mite 

causes brown discolouration even in fully developed grains. This leads to deterioration in paddy grain 

quality. 

Before sheath mite enters into developing grains, it is also present on midrib of leaf sheath and leaf and 

causes brownish, longitudinal specks. It completes life cycle in 10 days. 

15


ORGANOPHOSPATES 

16 

INSECTICIDES USED IN RICE PEST 

MANAGEMENT 

Quinalphos: C H N O PS. O, O-diethyl O-quinoxaline-2-yl phosporothioate. It is a contact and stomach 

12 15 2 3 

insecticide and acaricide with good penetrative properties. It is effective against sucking insects and 

lepidopterous larvae particularly of cotton and rice. The acute oral LD and dermal LD for rats are 62- 

50 50 

137 mg/kg and 1250-1400 mg/kg respectively. It is toxic to honeybees. It is formulated as 25% EC, 5% 

granules and 1.5% dust. 

Phosalone: C H CINO PS . It is O, O-diethyl S- (6-chloro 1, 3 benzoxazole-2 (3H)-on-methyl) 

12 15 4 2 

phosphorodithioate or 3-O,-O, diethyl dithiophosphorylmethyl-6 chloro benzoxazolone. It is a contact 

insecticide and acaricide effective against a wide range of pest species. It is stable under normal storage 

conditions, compatible with most other pesticides and non-corrosive. It is safe to honey bees and natural 

enemies of insect pests. Formulated as 4% dust and 35% EC. LD for rat: oral 120-170mg/kg, dermal 

50 

1500 mg/kg. 

Monocrotophos: C H NO P. It is dimethyl (E)-1-methyl-2-methylcarbamoylvinyl posphate. It is incompatible 

7 14 5 

with alkaline pesticides. It is corrosive to iron, brass and drum steel. It is a fast acting insecticide and 

acaricide with both systemic and contact action used against a wide range of pests including mites, 

sucking insects, leaf eating beetles and bollworms. It persists for 7-14 days. It is highly toxic to birds and 

honeybees. Oral LD for rats is 14-23 mg/kg and dermal LD for rabbit is 336 mg/kg. Formulated as 

50 50 

36% SL. 

Chlorpyriphos: C H C NO PS. The chemical name is O,O-diethyl O-(3,5,6-trichloro-2-pyridyl) 

9 11 l3 3 

phosphorothioate. It is compatible with non-alkaline pesticides but corrosive to copper and brass. It has 

a broad range of insecticidal activity and used for the control of mosquitoes, flies, soil and foliar crop 

pests, household pests and animal pests. It is contact, non-systemic and has some fumigant action. It is 

non-phytotoxic and persists in the soil for 60-120 days. It is toxic to fish and shrimps. It is rapidly detoxified 

in the animal body. The acute oral LD for rats is 135-163 mg/kg. The formulations registered are 20% 

50 

EC, 10% granules and 1.5% DP. 

Acephate: C H NO PS. It is O, S-dimethyl acetylphosphoramideothioate. Acephate is a contact and systemic 

4 10 3 

insecticide with moderate persistence for 10-15 days and effective against aphids, thrips, leaf miners, 

saw flies and lepidopterous larvae. It is formulated as 75% SP. Acute oral LD for rats is 866-945 mg/kg; 

50 

dermal for rabbit is >2000 mg/kg. It is relatively safer to many natural enemies compared to other 

organophosphates. 

Fenitrothion: C 9 H 12 O 5 NPS. It is O, O-dimethyl O- (3-methyl -4 nitrophenyl) phosphorothioate. It is a contact 

and stomach insecticide, selective acaricide but of low ovicidal activity. It is toxic to bees and fish. It is a 

broad-spectrum insecticide used for the control of mites, mosquito larvae, bed bugs, poultry lice,


ectoparasites of livestock and pet animals. Formulations registered are 5% DP, 40% WP, 50% EC, 5% G, 

2% spray, 20% OL. Oral LD for rats is 250 mg/kg and dermal for mice is > 3000 mg/kg. 

50 

Dichlorvos (DDVP): C H C1 O P. It is 2,2-dichlorovinyl dimethyl phosphate. It is a contact and stomach 

4 7 2 4 

poison with fumigant and penetrant action. It brings quick knock down effect. It is moderately toxic 

to fish but highly toxic to bees. Soon after application in leaves it gets hydrolyzed to harmless 

dimethyl phosphoric acid and dichloroacetaldehyde, which decomposes and evaporates. Therefore, 

it does not leave any residue and can be used on all crops until shortly before harvest. It is used in the 

control of household pests lepidopterous larvae, sucking insects etc. It is available in India as 76% SC. 

Oral LD for albino male rat 80 mg/kg, for female 56 mg/kg; dermal-albino male rat 107 g/kg, and 

50 

female rat 75 mg/kg. 

Fenthion: C H O PS . It is O, O-dimethyl, O-3 me-thyl-4-methylthiophenyl phosphorothionate. It is a 

10 15 3 2 

systemic and contact insecticide with high persistence. In the plant it is oxidized to sulfoxide and sulfone, 

which are insecticidally active. It is harmful to bees. It is effective against a wide variety of pests 

particularly fruit flies, mango nut weevil, etc. Registered formulations are 82.5 EC, 2% G and 2% spray. 

LD for rat: oral 215-245 mg/kg; dermal 320-330 mg/kg. 

50 

Phorate: C H O PS . It is O,O-diethyl S-(ethylthio- methyl) phosphorothiolothionate. It is a systemic 

7 17 2 8 

insecticide mainly used for soil application as granules. It has contact and fumigant action and to 

some extent nematicidal and acaricidal action also. It does not persist for a longer period and gets 

metabolically oxidized yielding phosphorothioate and sulfone, which are readily hydrolysed. It has 

been found effective against sorghum shoot fly and rice gall midge. Formulated as 10% G. LD for 50 

rat: oral 16 to 37, dermal 2.5 to 6.2 mg/kg. 

Phosphamidon: C H O NCIP. It is 2 - Chloro - 2 – diethyl carbamoyl – 1 - methyl vinyl dimethyl 

10 19 5 

phosphate.It is a systemic poison and has relatively less contact action. It is relatively less toxic to 

fish but toxic to bees. Useful in the control of sucking pests, leaf miners, certain mites etc. Though 

compatible with most pesticides, its biological activity is reduced with copper oxychloride. LD for rat: 

50 

Oral 17.9 - 30 mg/kg, dermal 374 - 530 mg/kg. Its use in India is being phased out. 

Ethoprophos: C H O PS It is O-ethyl S.S-dipropyl phosphorodithioate. It is an ether derivative. It is very 

8 19 2 2. 

stable in water up to 100° but is rapidly hydrolysed in alkaline media at 25°. Ethoprophos is a nonsystemic, 

non-fumigant nematicide and soil insecticide used at rates of 1.0 kg a.i./ha for most crops. The 

acute oral LD for albino rats is 62 mg/kg; the acute dermal LD for albino rabbits is 26mg/kg. It is 

50 50 

formulated as granules and EC. 

CARBAMATES 

Carbaryl: C |2 H H NO 2 It is 1 - napthyl N - methyl carbamate. It was introduced in 1956. It is a contact 

insecticide with slight systemic action. It is not generally phytotoxic up to 2 kg a.i./ha and is compatible 

with most pesticides except Bordeaux mixture, lime sulphur and urea. It is effective against a wide 

spectrum of insect pests of crops particularly of cotton. It does not kill mites. Application of carbaryl 

17


on apple trees causes fall of young fruits. It is formulated as 5% or 10% dust, 4% granule and 

50% WP or 85% SP or 40% LV and 42% Flow. 5% dust controls ticks on cattle, sheep and dogs and 

poultry lice. Sevidol granule recommended for control of rice pests is composed of 4% in each of 

carbaryl and gamma HCH. Sevimol 40 LV is a product containing 40% carbaryl plus molasses. 

Carbofuran: C H NO . It is 2,3-dihydro - 2, 2-dimethyl 7 benzofuranyl methyl carbamate. It is a 

I2 15 3 

systemic insecticide and nematicide effective against sucking and soil inhabiting pests and used in 

the control of sorghum shoot fly. Established crop tolerances are: 0.5 ppm in forage, 0.1 ppm in grain; 

0.2 ppm in rice and rice straw. Formulated as 50% SP and 3% granule. LD for rat: oral 8.8 to 14.1 

50 

mg/kg; dermal 10,200 mg/kg. Carbofuran application induced growth stimulation in cotton, rice, 

tobacco, sorghum and corn. 

Carbosulfan: C H N O S. It is 2, 3 - dihydro - 2, 2 - dimethyl benzofuran - 7 - yl (dibutylaminothio) - 

20 22 2 3 

methyl carbamate. It is effective against a broad spectrum of pest species on various crops. It is 

metabolized in plants to carbofuran and 3 -hydroxycarbofuran. Its registered formulations are 25% DS 

and 25% EC. Its acute oral LD5 for rat 185 - 250 mg/kg; dermal for rat > 2000 mg/kg. 

0 

BPMC or Fenobucarb: C H NO . It is 2-jec-butylphenyl methyl-carbamate. It is unstable to alkali and to 

12 17 2 

concentrated acid. It is an insecticide used to control hoppers on rice. The acute oral LD is: 410 mg/kg 

50 

for rats; dermal LD for mice is 4200 mg/kg. It is formulated as EC, dust and granules. 

50 

MIPC or Isoprocarb: C H NO . It is 2-isopropylphenyl methylcarbamate or o- cumenyl methylcarbamate. It 

11 15 2 

is compatible with most conventional pesticides, but should not be combined with products having an 

alkaline reaction nor used within 10 days prior to or after application of propanil. Isoprocarb is a contact 

insecticide of low mammalian toxicity effective against pests of rice, for the control of aphids, leafhoppers, 

capsid bugs and other pests of deciduous fruit and other crops. It has a moderately long residual activity. 

The acute oral LD is 403-485 mg/kg for rats. The acute dermal LD for male rats is > 500 mg/kg. It 

50 50 

is harmful to honey bees. The formulations include wettable powder, EC, thermal fog, granules and dusts. 

INSECT GROWTH REGULATOR 

Buprofezin: C 16 H 23 N 3 OS. It is 2-tert - butylimino - 3 - isopropyl - 5 - phenylperhydro - 1,3,5 - 

thiadiazin -4 - one. It has contact and stomach action. Effective against mealy bugs, whiteflies, 

scales, plant hoppers, etc. The eggs laid by treated insects are sterile. Oral LD 50 for rat is > 2000 

mg/kg; dermal for rat is > 5000 mg/kg. 

PHENYL PYRAZOLES 

Fipronil: C 12 H 4 C1 2 F 6 N 4 OS. It is chemically (±) -5 -amino - 1 - (2,6 - dichloro -trifluoro - g_ tolyl) - 4 

trifluoro methyl) = sulfinylpyrazole - 3 - carbonitrile. It is an insecticide and acaricide effective against 

pests of rice in India. Acute oral LD 50 for rat is100 mg/kg, dermal for rat is > 2000 mg/kg. Its 

registered formulations in India are 0.3% G and 5% SC. 

18


Ethiprole: C 13 H 9 C 12 F 3 N 4 OS. The chemical name is 5-amono-1-(2-6-dichloro-4-(trifluromethyl)-4ethylsulfinyl-1H-pyrazole-3-carbonitrile. 

It differs from fipronil the major phenyl pyrazoles insecticide, 

only in an ethylsulfinyl substituent replacing the trifluromethylsulfinyl moiety. It is an insecticide 

recommended for alfalfa, cotton, peanut, rice and soybean highly active on stink bugs, planthoppers 

and aphids.it is an inhibitor to neural transmission by GABA. It has low toxicity to fish and birds but 

affects silkworms. 

NEONICOTINOIDS 

Imidacloprid: C H C1N 0 . Chemically it is 1 - (6 - chloro - 3 - pyridylmethyl) - N nitroimidazolidin-2 - 

9 IO 5 2 

ylideneamine. It is a systemic insecticide with stomach and contact action. Controls sucking insects, 

soil insects, rice water weevil etc. Used as a seed dressing or foliar/soil treatment for control of 

pests of cotton, rice, etc. Acute oral LD for rat is 450 mg/kg; dermal for rat is > 5000 mg/kg. 

50 

Thiamethoxam: C H ClN O S (EZ)-3-(2-chloro-1, 3-thiazol-5-ylmethyl)-5- methyl-1, 3,5-oxadiazinan-4- 

3 10 5 3 

ylidene (nitro) amine. It is nitroguanidine or thiazole insecticide. It is slightly carcinogenic to rats. It has 

contact, stomach and systemic activity. It is recommended for the control of aphids, whitefly, thrips, rice 

hoppers, rice bugs, mealybugs, white grubs, leaf miners etc as foliar and soil insecticide in cole crops, 

vegetables, rice, cotton, fruits trees and other cereals. The formulations are FS, 70 WP, GR, SG, 25 WDG, 

and WS. Acute oral LD for rat is1563 mg/kg and dermal for rat is > 2000 mg/kg. 

50 

Thiacloprid: C H CIN S. It is (Z)-3-(6-chloro-3-pyridylmethyl)-1-3-thiazolidine-2-ylidenecynamide. It is an 

10 9 4 

insecticide and molluscicide. It has contact and stomach action with some systemic properties. It is new 

chloronicotinyl insecticide, targeted chiefly to control aphids in orchards and vegetables. It’s acute oral 

LD for rat’s is > 444 mg/kg. It is a possible carcinogen in the human beings. MRL for cereals is 

50 

0.02 mg/kg. 

NERISTOXINS 

Cartap: C 7 H 16 C1N 3 O 3 S 2 . Common name is Cartap hydrochloride. Chemical name is S, S - 2dimethylaminotri 

methylene) bis (thiocarbamate) hydrochloride or 1, 3 - Bis (carbomylthio) - 2 -(N, 

N-dimethylarnino) propane hydrochloride. It is systemic with stomach and contact action. It acts on 

the central nervous system by ganglionic blocking action resulting in paralysis, cessation of feeding 

and death due to starvation. It is effective against rice stem borer and leaf folder, sugarcane shoot 

borer, cabbage diamond back moth, etc. Its registered formulations in India are: 50 SP and 4 G. It’s 

acute LD 50 : oral (rat) male 345 mg/kg, female 325 mg/kg; dermal (mice) > 1000 mg/kg. 

Thiocyclam: C 5 H 11 NS 3 . It is N.N-dimethyl-l, 2, 3—trithian-5-ylamine. It is stable under ambient storage 

conditions. Thiocyclam is selective insecticide acting as stomach poison and by contact with a 7-14 d 

residual activity and capable of acropetal translocation. It is effective against lepidopterous and coleopterous 

pests, particularly Leptinotarsa decemlineata larvae on potatoes. The acute oral LD 50 is 310 mg/kg for 

male rats. It is moderately toxic to honey bees. It is formulated as SP, WSP and granules. 

19


ETHER DERIVATIVES 

Ethofenprox: C 25 H 2g O 3 . It is a non-ester pyrethroid introduced in 1987. It is a contact and stomach insecticide. 

It is effective against pests of rice, particularly BPH and leafhoppers. It is also effective against 

houseflies and cockroaches. Its registered formulation is 10% EC. Its acute oral LD 50 for rat is 42880 

mg/kg; dermal for rat > 2140 mg/kg. 

FERMENTATION PRODUCTS 

Spinosad: A natural source insecticide containing a mixture of two components derived from 

fermentation technology produced by Saccharopolyspora spinosa, a species of actinomycete. It is 

formulated as 48 SC and is active against Helicoverpa armigera, leafhoppers, aphids and whiteflis on 

cotton at 75 - 100 g a.i. /ha. 

DIAMIDES 

Flubendiamide: C 23 H 22 F 7 IN 2 O 4 S. It is 3-iodo-N-2(-mesyl-1-1-dimethylethyl-N-(4-(1, 2, 2, 2-tetrafluoro-1- 

(trifluromethyl) =ethyl)-Otolyl) phthalamide. It is a stomach poison. Flubendiamide has excellent fast 

acting and residual activity against a broad spectrum of lepidopterous insect pests including resistant 

strains. The fludendiamide treated larva discriminately contracts in size. It is safe to non-target organisms. 

Its acute oral LD 50 for rats > 2000mg/kg, dermal for rat is > 2000 mg/kg. It is a slight eye irritant 

but not skin irritant. The commercial formulation available is wettable powder. 

20


PRICIPLES OF INSECTICIDE USE IN RICE IPM 

Insecticide use is an indispensable evil in any crop ecosystem when one thinks in terms of ecological 

conservation. However, the following principles will, to a large extent, avoid the ill effects and help conserve 

biological and ecological diversity. 

Selection of proper insecticide and formulation 

The major factors that dictate the selection of an insecticide are the pest situation, stage of crop growth, 

availability of the chemical and its formulation, the cost of the insecticide, the likely benefit that will accrue 

due to usage of the insecticide in comparison with the other alternatives etc. 

Based on the experience gained in insecticide evaluation in rice, both as a part of lead research and 

coordinated programme, since 1966, when All-India Coordinated Rice Improvement Programme (AICRIP) 

was initiated, information on the spectrum of insecticide effectiveness against different insect pests of 

rice has been generated. The details are presented for spray formulations (Table 1) and for granular 

formulations (Table 2). 

EVALUATION METHODOLOGY 

In the All India Co-ordinated testing program the spray formulations were evaluated as high volume 

sprays by mixing with water @ 500 to 800 litres per hectare on need basis depending on the pest 

occurrence. The number of applications varied from 1 to 5 depending on pest intensity in a given location 

and season. The recommended plot size was 20-25 square meters. The granular insecticides were 

broadcast in standing water and the number of applications varied from 1 to 3 and rarely 4. The test 

insecticides were compared with a standard insecticide (usually monocrotophos / chlorpyriphos @ 500 g 

a.i./ha in case of spray formulations and carbofuran @1000 g a.i./ha, with respect to granules). 

The observations on different insect pests were recorded as per the standard procedures. In case of 

stem borer, the total tillers and dead hearts were counted in 20 hills per plot by following stratified 

random sampling in vegetative phase. The same procedure was followed at heading phase by counting 

white ears and panicle bearing tillers. In case of gall midge, silver shoots were enumerated along with 

total tillers. In all the above cases percentages were computed for judging the relative efficacy of insecticides. 

With regard to leaf feeding insects like leaf folder, rice hispa, case worm, swarming caterpillars, whorl 

maggot etc. total leaves and damaged leaves were enumerated to calculate percentage leaves damaged. 

Brown planthopper, whitebacked planthopper and green leafhopper were enumerated as total insects for 

each species (both nymphs and adults) present on 10 to 20 randomly selected hills per plot and relative 

number of insects present was the basis for judging the effectiveness of insecticides. Observations on 

important natural enemies of insect pests viz. egg parasitism in case of stem borers, important predators 

of BPH and WBPH such as green mirid bug, brown mirid bug, spiders as group were recorded under field 

conditions or after bringing samples to the laboratory. 

21


SPECTRUM OF INSECTICIDE EFFICACY 

Some of the spray formulations like monocrotophos, phosphamidon, cartap, and fipronil are effective 

against wide range of insect pests like stem borers, leaf folder, case worm, cut worm and army worms (all 

lepidopterans), brown planthopper, whitebacked planthopper, green leafhopper (all homopterans), rice 

hispa (coleopteran) and thrips (thysonopteran). These broad-spectrum insecticides have to be 

recommended in situations where many groups of pests are simultaneously present in rice ecosystem. 

This type of situation is common in many delta areas like Krishna-Godavari zone of Andhra Pradesh, 

Tunga Bhadhra areas of Karnataka, Tanjore delta of Tamil Nadu, Mahanadi delta of Orissa particularly 

during kharif season (Table 1). 

However, in areas like Punjab, Haryana, Assam, parts of Maharashtra (Karjat area) during kharif season 

and parts of Telangana in Andhra Pradesh, Mandya area of Karnataka, Coimbatore region of Tamil Nadu 

during rabi season, where stem borers and leaf folders are the major menace, the insecticides like cartap 

(both granules and spray), quinalphos, phosalone, chlorpyriphos, phosphamidon, triazophos sprays which 

have proven effective against both stem borers and leaf folders have to be preferred. Among the modern 

groups of insecticides, spinosad (a fermentation product containing spinosyn A and B), flubendiamide 

belonging to diamide group and indoxacarb belonging to oxadiazine group, which can check lepidopteran 

pests effectively and economically, have to be preferred. 

In situations, where BPH and WBPH are the major problems without significant presence of other pests 

particularly lepidopterans, the insecticides that have high degree of effectiveness against homopterans 

like imidacloprid, thiamethoxam, clothianidin (all neonicotinoids) can be economically used. However, in 

view of already widespread signals of resistance development in hopper pests in these endemic areas, 

this factor should be given due consideration. In this connection, detailed information has already been 

documented and readers are recommended to go through the Technical Bulletin “Neonicotinoid Insecticide 

Resistance in Agricultural Pests” by Krishnaiah et al., (2006) published by DRR, Rajendranagar, Hyderabad. 

As alternatives to neonicotinoids, phenyl pyrazoles like ethiprole, or organophosphates like acephate, 

monocrotophos or carbamates like carbaryl, carbosulfan BPMC, MIPC or neiristoxins like cartap or insect 

growth regulators such as buprofezin, or ether derivatives like ethofenprox, which can effectively check 

even neonicotinoid resistant populations at reasonable cost, are suggested. 

GRANULAR FORMULATIONS AGAINST INSECT PESTS 

Among granular formulations, carbofuran, carbosulfan, isazophos, and fipronil are broad-spectrum 

insecticides, which can be utilized in areas where both lepidopterans and homopterans are present. But 

in situations where lepidopterans like stem borers and leaf folder are problematic, cartap is the best 

insecticide followed by fenthion and thiocyclam. In areas, which are endemic to leafhoppers and planthoppers 

and where these are the major devastating pests, granular insecticides like BPMC and MIPC can be used 

followed by sprays of neonicotinoids and other alternative spray formulations; as sole dependence on 

granular formulations for the management of leaf- and planthoppers is not a suitable strategy in view of 

the cost involved (Table 2). 

22


Table1: Spectrum of toxicity of spray formulations against insect pests of rice 

Insecticide Group Rate 

(g a.i. ha) 

SB LF RHBPHWBPHCW GLH 

Quinalphos OP 500 ** *** ** * ** 

Phosalone OP 500 *** ** *** ** * * ** 

Monocrotophos OP 400 *** *** ** *** *** ** *** 

Chlorpyriphos OP 500 *** *** ** ** 

Acephate OP 750 * ** ** *** ** 

Fenitrothion OP 500 * ** * 

Phosphamidon OP 500 ** *** ** ** ** ** 

Fenthion OP 500 * *** ** * 

Dichlorvos OP 500 ** ** *** 

Triazophos OP 300 ** *** *** 

Carbaryl CB750 * ** ** *** *** * ** 

MIPC CB500 * ** ** ** 

BPMC CB 500 * ** ** ** 

Carbosulfan CB500 * * ** ** ** 

Cartap NT 300 *** *** ** ** ** ** 

Ethofenprox ED 75 * * *** *** *** 

Fipronil PP 50 ** ** ** ** ** ** * 

Ethiprole PP 50 * * *** *** * 

Imidacloprid NN 25 * *** *** *** 

Thiamethoxam NN 25 * *** *** *** 

Thiacloprid NN 120 * * ** ** ** 

Buprofezin GR 100 ** ** ** 

Indoxacarb OD 30 ** ** 

Spinosad FP 56 *** *** 

Flubendiamide DA 25 *** *** 

* Moderately effective ** Effective *** Highly effective 

NT: Neiristoxin OP: Organophosphate CB: Carbamate 

NN: Neonicotinoid PP: Phenyl pyrazole GR: Growth regulator 

DA: Diamide ED: Ether derivative FP: Fermentation product 

OD: Oxadiazene SB: Stem borers LF: Leaf folders 

RH: Rice hispa BPH: Brown Planthopper CW: Cutworm 

GLH: Green leafhopper WBPH: Whitebacked planthopper 

23


GALL MIDGE MANAGEMENT WITH GRANULAR INSECTICIDES 

For the management of gall midge, which is endemic in many deltas and certain special areas like Telangana 

in A.P, Ranchi area of Bihar, states like Orissa, Goa, and Manipur along with many coastal areas, resistant 

varieties are popular. But the problem of biotypes in the insect and lack of other desirable traits like grain 

quality in the resistant varieties etc. are the limitations. Hence, farmers have to resort to insecticide 

application particularly in late sown and late transplanted situations. 

The past results from coordinated trials and lead research have clearly shown that spray formulations are 

ineffective against gall midge except chlorpyriphos which is moderately effective at recommended dosage 

of 500 g a.i./ha. Among the granular insecticides carbofuran, phorate, chlorpyriphos, isazophos and 

quinalphos are moderately good in reducing the silver shoot incidence. It also came to light that cartap 

and thiocyclam, which are neiristoxins, have poor potential toxicity to gall midge (Table 2). 

24 

Table 2: Spectrum of toxicity of granular formulations against insect pests of rice 

Insecticide Group 

Rate 

(g a.i./ ha) 

Carbofuran CB750 *** ** *** ** *** *** ** 

Carbosulfan CB1000 ** ** ** ** * *** *** *** 

MIPC CB1000 ** * *** ** ** 

BPMC CB 1000 * * ** ** ** 

Phorate OP 1250 ** *** ** ** ** 

Quinalphos OP 1000 *** *** 

Fenthion OP 1000 ** ** ** *** 

SB GM WM LF RHBPHWBPHGLH 

Ethoprop OP 1000 ** * * * * * 

Chlorpyriphos OP 1000 ** *** ** * * * * 

Isazophos OP 600 *** *** ** *** *** ** *** 

Cartap NT 750 *** *** ** ** ** 

Thiocyclam NT 750 *** *** ** ** *** 

Fipronil PP 75 ** *** ** ** ** ** ** ** 

* Moderately effective ** Effective *** Highly effective 

PP: Phenyl pyrazole OP: Organophosphate CB: Carbamate 

NT: Neiristoxin SB: Stem borer GM: Gall midge 

WM: Whorl maggot LF: Leaf folder RH: Rice hispa 

BPH: Brown planthopper WBPH: Whitebacked planthopper GLH: Green leafhopper

Methods of insecticide application 


Method of insecticide application greatly influences the toxicity of insecticide to target pests and also in 

minimizing the adverse effect on natural enemies. 

SEED TREATMENT 

Detailed experiments under controlled glasshouse conditions as well as field conditions clearly showed 

that soaking sprouted rice seed in 0.2% emulsion of chlorpyriphos for 3 hours before sowing can guard 

the nursery from gall midge damage through out the nursery period. However, due to slight phytotoxicity 

of the insecticide reducing the nursery stand by about 10%, it can be recommended to the farmers in gall 

midge endemic areas with the caution about the reduced plant stand in the nursery. 

SEEDLING ROOT DIP 

Transplanting is common practice in many rice growing areas. This simultaneously offers the possibility of 

dipping the roots of seedlings in insecticide emulsions or solutions to ward off the transplanted crop from 

early stage pests like gall midge, stem borer and whorl maggot. Out of the 30 insecticide formulations 

evaluated as seedling root dip treatments, chlorpyriphos as 0.02% emulsion with a normal dipping period 

of 12 hours could effectively reduce the damage caused by gall midge, stem borer and whorl maggot. 

Logically this should also help conserve natural enemies like spiders, which colonize rice fields immediately 

after transplanting as the insecticide was confined only to root portion of the crop. 

However, chlorpyriphos as seedling root dip could not effectively check hoppers like GLH, WBPH and some 

times BPH, which start colonizing rice crop in early stages after transplanting. Hence, efforts were directed 

to this aspect and among several insecticides tested, carbosulfan 0.02% emulsion was the best and 

effective treatment against all the three hoppers. Therefore, a logical combination of chlorpyriphos 0.01%+ 

carbosulfan 0.01% was found effective against the whole pest complex in early stages after transplanting. 

As 12 hour dipping period is too long under practical field conditions, it can be reduced to 3 hours by 

adding 1% urea in the insecticide emulsion/solution. 

ROOT ZONE APPLICATION OF INSECTICIDES 

Rice is probably the only crop that offers anaerobic conditions in the root zone, due to its submergence 

under normal transplanted and irrigated conditions. Attempts to place the insecticides in the root zone 

either as solids or as liquids immediately after transplanting revealed that carbofuran granules @ 1.0 kg 

a.i./ha were the most effective and protected the crop from stem borers, gall midge, whorl maggot as well 

as GLH upto 90 days and the efficacy was equal to 3 granular broadcasts in standing water given at 20 

days interval. 

When insecticides were placed in the root zone, the persistence of insecticides was increased due to the 

minimization of losses by oxidation, vaporization, run-off along with flowing water and exposure to sunlight 

25


etc. Encouraged by this, attempts were made to apply insecticides more easily as liquids by mixing wettable 

powders and EC formulations with water in to the root-zone successfully with different applicators. 

Further attempts to coat urea super granules with wettable powders of carbofuran either with coal tar or 

with neem oil and placing the coated material in the root zone were also successful. This could place both 

insecticide and the urea fertilizer in the root zone with the same labour cost and results in supply of both 

N and insecticide to the crop very efficiently. 

Predators like spiders, mirid bugs, egg, larval and pupal parasitoids of all foliage feeding pests like leaf 

folder, hispa and also stem borers etc. could be conserved by root zone application of insecticides in this 

manner. 

Management of pest resurgence 

It is very well documented in literature that resurgence of insect pests in rice has to be very carefully dealt 

with. This problem was more acute in BPH and WBPH. But in future this is going to be problem in case of 

other pests like leaf folder also. 

BPH AND WBPH ENDEMIC AREAS 

Synthetic pyrethroids like deltamethrin, cypermethrin, fenvalerate and more recent molecules like beta 

cyfluthrin and lambda cyhalothrin have been found to increase the populations of BPH and WBPH invariably 

and to significantly higher levels than in untreated plots. The reasons for the resurgence of these pests 

could be multifarious including reduced competition, destruction of natural enemies, reproductive stimulation 

of the insect pests either directly due to contact with insecticides or indirectly through changed physiology 

of the host plant. Hence, it has been strongly advocated that synthetic pyrethroids should be avoided in 

rice ecosystem at all costs. Further, synthetic pyrethroids possess poor potential toxicity to other insect 

pests like stem borers etc. barring leaf folders. Hence, the synthetic pyrethroids are not indispensable in 

rice ecosystem. 

In India, the problem of planthoppers is increasing year after year. These pests are spreading to new 

areas in indo-gangetic belt from their traditional areas in southern parts of the country. So, with the use 

of synthetic pyrethroids in areas where BPH and WBPH are not currently the major pests may also 

turnout to be the hot spots for hoppers in future. This point is to be viewed with utmost caution. 

OTHER PESTS, PARTICULARLY LEAF FOLDER 

Among the other pests, the problem of resurgence will be more acute in leaf folders. Previously, there 

were stray cases of relatively higher leaf folder damage in plots treated with granular insecticides like 

phorate and some times carbofuran. Later observations confirmed that these two granular formulations 

do cause resurgence of leaf folder. These granular insecticides are very essential component of insect 

pest management strategy in rice, because, granules have to be applied in gall midge endemic areas if 

susceptible cultivars and late-planted conditions are unavoidable. Under these situations, the farmers 

26


are to be cautioned regarding the possible upsurge of leaf folder following the granular application 

against gall midge. 

Of late, neonicotinoid insecticides like imidacloprid, thiamethoxam and clothianidin are extensively used 

against BPH in endemic areas. In these conditions also there are observations of high leaf folder incidence 

compared to untreated plots. Even, if a quick conclusion need not be arrived at that all neonicotinoids 

cause resurgence of leaf folder, the situation demands more observations confirming the ineffectiveness 

of neonicotinoids against leaf folder, on the part of the rice entomologists and caution for rice farmers. 

COMBINATION PRODUCTS: THE SCOPE AND RISK 

The latest groups of insecticides like neonicotinoids, diamide compounds like flubendiamide, oxadiazines 

like indoxacarb and fermentation products like spinosad and relatively older molecules like synthetic 

pyrethroids are effective at low dosages (10 to 100 g a.i./ha) compared to 500 g a.i./ha in case of OPs 

and carbamates. But these tend to be more specific. For instance, neonicotinoids are effective against 

homopterans or sucking pests while other groups are effective against lepidopterans. Therefore, by 

preparing the combination products with one molecule of neonicotinoids and another molecule from 

lepidopteran effective groups, it is possible to effectively check the whole pest spectrum attacking rice 

crop. Accordingly, the thrust is to evaluate and select suitable combination products for each pest situation 

depending on the spectrum of toxicity of these individual compounds. Thus, there is ample scope in this 

direction for management of insect pests in general and rice pests in particular. Some of the latest 

combination products under evaluation along with their effectiveness against different rice pests are 

presented. (Table 3&4). 

However, the risk involved with combination products is high toxicity to natural enemies viz., both predators 

and parasitoids. At times, the combination products may be aimed at lepidopterans but they may cause 

harm to predators of leaf and planthoppers. Hence, a thorough evaluation of these combination products 

against the whole complex of natural enemies is essential before recommendation. 

Combining insecticides with other methods 

Insecticides alone are not the panacea for pest management in rice like any other agro-ecosystem. 

Insecticide use should be suitably integrated with other methods like natural enemies, sex pheromones, 

resistant varieties, cultural methods etc. 

AWARENESS OF TOTALITY OF RICE CROP AS AN ECOSYSTEM 

The awareness and the consciousness that rice crop or for that matter any other crop as an ecosystem is 

and should be the prime guiding principle whenever some interference with any of the methods of pest 

management including insecticide use is decided. For instance, when leaf mite and /or panicle mite are 

the problems in an area, then application of acaricides like dicofol, diafenthiuron, abamectin, milbemectin 

etc is very much essential. Similarly, when the diseases like sheath blight or sheath rot are prevalent 

27


Table 3: Spectrum of toxicity of combination products of insecticides against rice insect pests 

Combination product Group 

Ethiprole 40% + 

Imidacloprid 40% 

PP & NN 100 ** *** *** ** 

Thiamethoxam 12.6% + 

Lambda cyhalothrin 9.4% 

NN & SP 44 ** ** ** * * * 

Indoxacarb 7.5% + 

Lambda cyhalothrin 4% 

OD & SP 46 ** *** * * 

Acetamiprid 0.4% + 

Chlorpyriphos 20% 

NN & OP 510 * ** * * 

Profenophos 40% + 

Cypermethrin 5% 

OP & SP 440 * ** 

Chlorpyriphos 50% + 


OP & SP 344 * ** 

Beta cyfluthrin 5% + 

Imidacloprid 5% 

SP & NN 30 * ** * * 

Acephate 45% + 


OP & SP 500 * ** * * * 

28 

Dosage 

(g a.i./ha) 

Stem 

borer 

Effectiveness against pests 

Leaf 

folder 

Hispa Brown 

plant 

hopper 

White 

backed 

plant 

hopper 

Green 

leaf 

hopper 

* = moderately effective ** = effective *** = highly effective 

PP = Phenyl pyrazole NN = Neonicotinoid SP = Synthetic pyrethroid 

OP = Organophosphate OD = Oxadiazine 

along with insect pests like BPH and WBPH, or stem borer in heading phase of the crop, in those 

circumstances, the fungicides like edifenphos or IBP, which have some insecticidal properties, have to be 

used. In these circumstances, these are going to have adverse effect on natural enemies of insect pests. 

This type of information need to be generated and made available to the farmers for their guidance and 

corrective measures. 

COMBINING INSECTICIDE USE WITH VARIETAL RESISTANCE 

Donors and varieties with high level of resistance are available only for gall midge followed by moderate 

to good level of resistance for BPH, WBPH and GLH. Very few varieties with low level of resistance are

Insecticide 

Dosage 

(g a.i./ha) 


Table 4 : Influence of some combination products on stem borer and leaf folder 

Stem borer Leaf folder 

(% DH) (ADL/10 h) 

55 DAT (% WE) 55 DAT 70 DAT 

Grain yield 

(Kg/ha) 

Acephate 45% + 


500 2.1a 6.7ab 1.2a 3.0ab 4293a 

BPMC 300 g a.i. + 

Fipronil 10 g a.i. 

310 7.3b 7.5b 9.5b 12.7b 3725c 

Betacyfluthrin 12.5 g a.i. + 

Chlorpyriphos 250 g a.i. 

393 1.4a 7.4b 3.0a 8.5ab 3977b 

BPMC 230 g a.i + 

Chlorpyriphos 320 g a.i 

550 3.4a 7.0ab 34.2c 8.2ab 4040ab 

Monocrotophos 500 1.3a 5.4a 14.0b 1.5a 3914bc 

Untreated control 11.5b 9.7c 59.5d 32.7 3093d 

(Krishnaiah et al 2003a) 

Note: figures in a column followed by same letter are not significantly different at p=0.05 by l.s.d. 

available for YSB, and few donors for leaf folders. This emphasizes the importance of combining insecticide 

use along with varietal resistance. 

In the regions like many coastal areas of Orissa, A.P., Tamil Nadu, Kerala and Karnataka, where gall midge 

is the major problem, this can be taken care by resistant varieties alone. In such cases, other pests like 

leaf folder and stem borer need to be managed by selection and use of appropriate insecticides. 

In areas where BPH and WBPH are the major problems use of moderately resistant varieties alone is not 

adequate to protect the crop from these pests. Varietal resistance should be supplemented with need 

based insecticide use depending on the pest pressure. However, the quantum of insecticide use is much 

less compared to that used in the protection of BPH and WBPH susceptible varieties. In case of GLH, 

moderate to high level of resistance is available but the number of resistant varieties available are very 

few and are not sufficient to meet all ecological situations where, tungro is a problem for which GLH is 

notorious as vector. Therefore, in tungro endemic situations, insecticide use is a must. 

SAFE-GUARDING NATURAL ENEMIES FROM INSECTICIDES 

The biodiversity of natural enemies of all the major pests in rice ecosystem is very wide. The egg, larval 

and pupal parasitoids of lepidopteran and coleopteran pests and wide variety of predators like mirid 

bugs, coccinellids, staphylinids and few hundreds of species of spiders are present in rice ecosystem. 

29


Hence, any insecticide use is likely to harm one or other groups of these natural enemies. Studies on 

potential toxicity of important insecticides to major natural enemies under laboratory conditions are a pre 

requisite for avoiding the insecticides with high ecological damage. 

Secondly, the timing of insecticide use is very important. For instance, the inundative release of parasitoids 

like Trichogramma aimed against egg stage of leaf folder should not coincide with insecticide use against 

BPH and WBPH, which simultaneously occur in the same crop ecosystem. 

COMBINING PHEROMONES WITH INSECTICIDE USE 

In rice, pheromone technology has come to a stage of practical application only in case of YSB. Pheromones 

can be used in rice ecosystem for 1) monitoring the levels of pest populations to decide the best time of 

insecticide application 2) for mass-trapping 3) male confusion technique. 

For the purpose of monitoring, trap-capture thresholds that establish the relationship between numbers 

of male moths caught per week in the traps and the damage that is likely to occur with the pest population 

present in the field are already established in case of YSB. Hence, in areas where YSB alone is the 

problem, insecticides already suggested against stem borer can be coupled with pheromone trap capture 

thresholds 

Mass trapping of male moths to reduce their population below a critical level, which reduces the total 

number of fertile eggs laid by females and finally results in lower actual damage as dead hearts or white 

ears, has been successful. Sleeve traps each with 10 mg of pheromone @ 20 traps/ ha have been found 

effective against YSB. However, the male confusion technique did not workout to be practical or economical 

in case of YSB. 

If YSB is the only problem in a rice crop, mass trapping technology can be very well coupled with use of 

appropriate insecticides on need basis. If other pests like leaf folders or BPH and WBPH are also present 

in rice crop ecosystem, then selection of proper insecticide(s) that can take care of all the problems may 

work out to be practical and economical. 

30


EFFECTIVENESS OF INSECTICIDES AGAINST 

RICE INSECT PESTS 

A. INSECTICIDE EVALUATION AGAINST MAJOR PESTS 

i) BROWN PLANTHOPPER, Nilaparvata lugens (Stal) 

After BPH became a major insect pest attacking rice crop in India in 1972, late Dr. M. B. Kalode took lead 

in evaluating insecticides against this pest. With the help of his student, Dr. Kalode studied the biology of 

this pest and assessed the potential toxicity of several spray and granular formulations available at that 

time (Venkataswamy & Kalode, 1980). Among 24 granular formulations (at 2 kg a.i./ha) and 38 spray 

formulations (0.05% a.i.) evaluated against nymphs by caging method., isoprocarb (Mipcin) and carbofuran 

granules and sprays of carbaryl and monocrotophos were the best for quick initial effectiveness and 

persistent toxicity. Among other insecticides terbuphos, disulfoton granules, sprays of thiocyclam and 

cartap were the next best in the order. Initial recommendations of the best insecticides were also made to 

the farmers based on the study. Later, Krishnaiah et al., (1982a and b) made detailed toxicological 

investigations on brown planthopper. Among the 14 spray insecticides at 0.05%, carbosulfan, BPMC had 

good knock down effect but carbosulfan persisted for a longer period. Carbosulfan also exhibited high 

contact toxicity when tested by Potters Tower method. Among the insecticides evaluated for their downward 

translocation property in rice plants by spraying on the upper portion and confining the BPH to the lower 

unsprayed position, BPMC was identified to possess that property. But it persisted only for 5 days. 

Chlorpyriphos, isofenphos, dicrotophos, carbofuran, monocrotophos, demeton–o-methyl, carbaryl and 

isoprocarb showed no appreciable translocation. Ovicidal activity was assessed by spraying on plants 

containing one day old BPH eggs. Carbofuran, isoprocarb and BPMC @ 0.05% completely inhibited egg 

hatching. 

Later studies at DRR on comparative toxicity of synthetic pyrethroid, organophosphate and carbamate 

insecticides against BPH and GLH (Krishnaiah and Kalode 1988a) revealed that synthetic pyrethroids 

(deltamethrin, cypermethrin and fenvalerate) were less toxic to BPH compared to GLH. Of seven 

organophosphates and two carbamates, UC-54229 to BPH and chlorfenvinphos to GLH were more toxic 

than monocrotophos. 

Krishnaiah et al., (2004) continued their efforts to evaluate later generation insecticides like neonicotinoids 

and phenylpyrazoles against BPH, WBPH and GLH. Neonicotinoids like imidacloprid, thiamethoxam and 

thiocloprid were toxic to BPH, WBPH and GLH, while phenyl pyrazoles like fipronil and ethiprole exhibited 

good toxicity to BPH and WBPH but were almost non toxic to GLH at 25 to 50 g a.i./ha, the normally 

recommended dose for these insecticides (Table 5). 

With the developments on insecticidal evaluation at DRR, Prakasa Rao and PRM Rao at CRRI Cuttack also 

evaluated several insecticides for their effectiveness and suitable methods of application (Rao and Rao 

1979, 1981 and 1982). Carbofuan, BPMC and isoprocarb were good ovicidal agents and also effective 

31


32 

Table 5 : PT values of neonicotinoids and phenyl pyrazoles for BPH, WBPH and GLH 

Insecticide Conc. (ppm) 

Persistent toxicity at 24 hours after release 

BPHWBPHGLH 

Thiamethoxam 25 2042cd 1811b 1483bc 

Imidacloprid 25 2166bc 1811b 1548ab 

Fipronil 50 2264ab 1975a 365f 

Monocrotophos (Check) 500 433h 931g 750e 

Acephate (check) 1200 1219g 1194f 1306d 

NB: The values in a column followed by the same letter are not significantly different at 

P= 0.05 according to l.s.d method. 

(Krishnaiah et al., 2004) 

against mobile stages. Among the insecticides phorate, BPMC and MIPC were found to have effective 

fumigant action. 

Carbofuran among granules and BPMC among sprays were confirmed for their effectiveness at other 

institutes also (Mohamed Ali et al., 1981; Uthama Samy and Suresh 1986; Krishnaiah and Butchaiah 

1987; Prakash and Bhattacharya 1993). Several field studies also confirmed the effectiveness of 

neonicotinoid compounds like imidacloprid and thiamethoxam and phenyl pyrazole compounds like ethiprole 

at dosages as low as 25 to 50 g a.i./ha (Manjunatha and Shivanna 2001; Verma et al., 2003; Hegde 

2005). 

At IRRI, Philippines, several insecticides have been evaluated for their ovicidal activity against brown 

planthopper. Sprays of carbofuran, triazophos, azinphos–ethyl, propoxur, fenitrothion, carbosulfan (0.75 

kg a.i/ha) were good ovicidal agents (Heinrichs and Valencia 1978; Valencia et al., 1979; Basilio and 

Heinrichs 1981; Heinrichs and Valencia 1981). 

Studies in Malaysia (Lim 1971) revealed that carbaryl, monocrotophos, thiometon, dicrotophos, malathion, 

phosphamidon (all at 0.1% concentration) exhibited good knockdown effect against nymphs of BPH. 

Field studies showed that imidacloprid alone was effective against BPH while in combination with monosultap 

it could effectively check both BPH and the stem borer Chilo supressalis in China (Iwawa et al., 1998 and 

Tao et al., 2005). Fipronil was found effective against several pests including BPH and WBPH in China (Wei 

et al., 2001; Sun et al., 1996 and Wang et al., 1995). 

Studies on Buprofezin 

Buprofezin is an insect growth regulator and chitin synthesis inhibitor with stomach action and also having 

good persistence in rice. It has been found to be effective at dosages as low as 100 to 150 g a.i./ha. It has 

been found to be extremely safe to natural enemies of BPH and WBPH under field conditions (Zheng et


al., 1993; Huang and Pang 1992; Pan and Chui 1989; Huang et al., 1989). Bae et al., (1994) from Korea 

could successfully suppress the populations of BPH and WBPH when buprofezin was applied in later 

stages of plant growth. 

Several studies were made on physiological effects of buprofezin application in BPH. Bae and Hyun 

(1989) from Korea observed that buprofezin reduced adult lifespan if applied to the nymphs. Gu et. al. 

(1993) from China reported that buprofezin suppressed egg laying and decreased life span of adults. 

Application of buprofezin at low dosages affected several metabolic enzymes such as CarE, AcP, AkP, ASAT 

and ALAT which resulted in metabolic disorders both in males and females with serious disturbances in 

free amino acids present in BPH (Fan et. al. 1993). This has great practical significance as the free amino 

acid content in rice stems following the application of high dosages of N to rice crop increases and this is 

a serious predisposition of rice crop for enhanced multiplication of BPH in the field. 

Liu et. al. (1989) from China reported that the toxicity of buprofezin declines as the nymphal stages of 

BPH advance. Histological observations revealed that destruction of chitin lamellae in the endocuticle 

and other organs rich in chitin was the main cause of moulting inhibition due to buprofezin. Kobayashi et 

al., (1989) from Japan observed that the insecticide buprofezin elevated the level of moulting harmone 

(ecdysone) and retarded the fall of ecdysterone in treated nymphs during 33 to 48 hours following the 

topical application. The fall in ecdysterone adversely affected old cuticle digestion and new cuticle deposition. 

Thus, buprofezin interferes by several ways with the physiology of treated insects but the death occurs 

only at the time of moulting showing that interference with the moulting process is the main mode of 

action in BPH. 

ii) WHITEBACKED PLANTHOPPER Sogatella furcifera (Horvath) 

Zafar (1982) from Pakistan identified isoprocarb and carbaryl as effective (1.25 to 2.125 kg formulation 

/ha) against WBPH. Krishnaiah and Kalode (1986c) carried out detailed insecticide evaluation studies 

under green house conditions, which involved 33 spray formulations and 7 granular formulations against 

nymphs of WBPH. Among sprays carbosulfan, fenitrothion, isoprocarb, were most effective, while carbosulfan 

was the most persistent compound. Dichlorvos was also effective under field conditions (Khan and Kushwaha 

1990). Carbforuan was the best granular insecticide both for knockdown kill as well as persistent toxicity. 

In field trials in Punjab, isoprocarb, quinalphos, ethion, fenitrothion and fenthion were found effective at 

500 g a.i./ha (Jaswant Singh et. al. 1988). The effectiveness of carbofuran at 1 kg a.i./ha was also 

confirmed under field conditions by others. Cartap as granules was also moderately effective (Panda and 

Shi 1988; Roshan Lal 2000; Sontakke and Senapati 1997). Phosphamidon (0.05%) was found to be 

ovicidal against WBPH (Ramaraju et. al. 1987). 

Flufenoxuran, a chitin synthesis inhibitor at 600 ppm was found to be ovicidal and also caused morphological 

deformities in hatched nymphs of WBPH. The deformed adults resulted when the nymphs were treated 

with this compound (Mani and Gopalan 1991). 

33


iii) STEM BORERS 

Among the stem borers that infest rice crop in India, yellow stem borer Scirphophaga incertulas is the 

most important. This insect is not amenable for artificial rearing in the laboratory. Rearing under greenhouse 

conditions on its natural host, rice plant, has limited scope for mass multiplication, owing to requirement 

of huge space, long time and big effort even to get very limited insect culture. Hence, the information on 

insecticide efficacy against yellow stem borer has been generated under field conditions. However, under 

field conditions along with YSB, other stem borers like white stem borer S. innotata, dark headed borer 

Chilo suppresalis, and pink stem borer Sesamia inferens are also present. As the symptoms caused by 

these different stem borers in vegetative phase (dead hearts) and heading phase (white ear heads) are 

similar, the effectiveness of insecticides reported in the literature reflects on the totality of stem borer 

complex and not necessarily to yellow stem borer alone. Along with stem borer, other pests like leaf folder 

and gall midge are also present in certain situations. 

GRANULAR FORMULATIONS 

Both granular formulations and spray formulations were extensively evaluated against stem borer. 

Subramanian et al., (1981) observed that BPMC granules at 2 kg a.i./ha were at par with standard check 

carbofuran (0.75 kg a.i./ha). BPMC was effective in Philippines (Heinrichs et al., 1986). Chlorpyriphos 5G, 

carbofuran 3G and diazinon 10 G were effective against over-wintering larvae in Pakistan (Ul-Haq and 

Inayatullah 1990). Gubbaiah et al., (1995) reported that cartap 4 G at 0.75 kg a.i./ha was at par with 

carbofuran 0.6 kg a.i./ha. Krishnaiah et al., (1996) reported that granules of ethoprophos and isazophos 

in addition to cartap (each at 1 kg a.i./ha) were more effective than the check insecticide carbofuran 

against stem borer and also leaf folder. Khan and Khaliq (1989) from Pakistan confirmed the effectiveness 

of cartap granules. Sontakke and Dash (2000) observed that chlorpyriphos granules (1kg a.i/ha) were 

effective against stem borer. Krishnaiah et. al. (2003a) reported that carbosulfan (1 kg a.i./ha) was also 

as effective as check insecticide carbofuran (1 kg a.i./ha) against this pest. 

SPRAY FORMULATIONS 

Among the spray formulations, furathiocarb, pyridaphenthion, BPMC (0.75 kg a.i./ha) and ethofenprox 

(0.05 kg a.i./ha) were moderately effective against stem borers while, pyridaphenthion and ethofenprox 

exhibited moderate effectiveness against leaf folder and were similar to chlorpyriphos (0.5 kg a.i./ha) 

(Krishnaiah et al., 1996). Triazophos and two new formulations of quinalphos (20 AF and 20 CS) at 0.5 

kg a.i./ha were found effective against stem borer. Later studies (Krishnaiah et. al. 2003a) indicated that 

the combination product viz., acephate 45% + cypermethrin 5% (500 g a.i./ha); beta cyfluthrin 1.25% 

+ chlorpyriphos 25% at 393 g a.i./ha; BPMC 23% + chlorpyriphos 33 % at 550 g a.i/ha and BPMC 30% 

+ fipronil 1% (at 310 g a.i/ha) were at par with standard check monocrotophos against stem borer and 

leaf folder. Dash and Mukherjee (2003) observed that silafluofen at 0.1 kg a.i./ha was at par with check 

insecticide chlorpyriphos (0.5 kg a.i./ha) against stem borers. Misra and Parida (2004) screened several 

34


combinations of insecticides against stem borer and observed that the combinations like acephate 25% 

+ fenvalerate 3%, ethion 40% + cypermethrin 5%, profenophos 40% + cypermethrin 4% were effective 

in reducing dead heart as well as white ear head incidence. 

Recent studies in China and Pakistan revealed that fipronil 5 EC @ 66 g a.i./ha either as spray or as mixed 

with fertilizer and broadcast in water (Saljoqi et. al. 2002) or as spray at 22.5 g a.i./ha was effective in 

reducing the dead heart and white ear incidence (Zhu et al., 2002). 

OVICIDAL ACTION 

Effectiveness of some of the insecticides against yellow stem borer eggs has been reported mainly from 

laboratory studies. Chlorpyriphos @ 0.5 kg a.i./ha (Sharma & Singh 1995); monocrotophos and fenitrothion 

@ 0.04% concentration (Pandya et. al. 1987) were good ovicidal agents. Synthetic pyrethroids like 

Permethrin (0.0125%), cypermethrin (0.01%) and fenvalerate (0.01%) caused higher mortality of stem 

borer eggs than the check insecticide diflubenzuron (0.02%) (Raju et. al. 1988). 

iv) LEAF FOLDER 

Leaf folder is a complex of species. About 8 species of leaf folders have so far been recorded attacking 

rice. However, recent studies in DRR under co-ordinated trials revealed that Cnaphalocrocis medinalis is 

the most dominant species or the sole species in almost all situations throughout the country. Hence, the 

effectiveness of insecticides even under field conditions reflects the efficacy against C. medinalis. 

Insecticide evaluation against leaf folder has been a part of insecticide testing program of DRR (formerly 

AICRIP) almost since 1980 when leaf folder started becoming a major pest (DRR 1980-2006). A bird’s 

eye view of the entire results on the effectiveness of granular formulations and spray formulations of 

various insecticides revealed that among the granular insecticides cartap 4G is the most effective insecticide 

when applied at 0.8 to 1.0 kg a.i./ha. It continues to be effective even today. Among other granules, 

carbofuran was moderately effective at 0.75 to 1 kg a.i./ha in the beginning that is upto 1990. Subsequently, 

there were many instances of ineffectiveness of carbofuran against leaf folder. Among the spray 

formulations, chlorpyriphos, quinalphos, monocrotophos, phosphamidon, triazophos, dicrotophos, cartap 

(all at 0.5 kg a.i./ha) and ethofenprox (@ 0.05 to 0.1 kg a.i./ha) were effective. Thus revealing that leaf 

folder can be very easily managed by a wide range of spray formulations. 

Effectiveness of Cartap against Leaf Folder 

Sakai (1971) was first to evaluate cartap hydrochloride as insecticide against leaf folder in Japan under 

field conditions. Endo and Masuda (1981a & b) from Japan concluded that cartap spray at 6 days after 

peak adult appearance is the best method for LF management. Endo (1997) observed differences in 

susceptibility level of larvae and adults of LF to cartap, monocrotophos and acephate by topical application 

method. LD 50 of cartap to adults was lower than that for larvae, while reverse was the case with 

35


monocrotophos and acephate. The effectiveness of cartap (0.5 kg a.i/ha) was confirmed under field 

conditions recently also (Seetharamu et. al. 2005). 

Valencia and Heinrichs (1982) identified 23 insecticides as effective against eggs and larvae of C. medinalis 

under green house conditions. Sain et. al. (1987) evaluated 15 insecticides @ 0.5 kg a.i./ha as sprays 

and observed that chlorpyriphos, methyl parathion, monocrotophos and quinalphos as the most effective 

based on larval mortality assessed at 5 days after spray and leaf damage at 10 days after spray. 

Naik et al. (1993) from Bhubaneswar assessed the toxicity of commercial insecticide formulations against 

4th instar larvae and found that monocrotophos, quinalphos and phosphamidon were the most effective 

based on LC50 values. Triazophos @ 0.5 kg a .i. /ha was effective under field conditions for controlling 

the incidence of C. medinalis and M. patnalis in Karaikal, Pondichery (Nadarajan 1996). Ethofenprox was 

observed to be effective against larvae at one tenth of the concentration of monocrotophos (Jena et al., 

1992). Mishra et al., (1998) confirmed that ethofenprox at 100 g a.i./ha was on par with cartap 

hydrochloride @ 0.5 kg a.i./ha against larvae. Pandya et. al. (1999) reported that profenophos (0.5 kg 

a.i./ha) spray was effective against leaf folder under field conditions. 

Synthetic pyrethroids, in general, are highly effective against leaf folder at recommended dosages of 

12.5 to 50 g a.i./ha. But these are not recommended in rice ecosystem due to BPH resurgence, as BPH 

is also endemic in many rice growing tracts where the leaf folder is a problem. 

v) GALL MIDGE Orseolia oryzae (Wood-Mason) 

During 1960s spray formulations of insecticides like endrin and ethyl parathion were under recommendation 

against gall midge. However, systematic evaluation of granular formulations and spray formulations of 

insecticides under AICRIP Entomology programme (DRR 1970-2000) and intensive studies under 

greenhouse conditions (Kalode et al 1982a and b) led to the identification of granular insecticides like 

carbofuran, mephosfolan, chlorfenvinphos, quinalphos and phorate at 750 to 1000 g a.i./ha as effective 

against this pest. During this period the most important point that emerged was that spray formulations, 

in general, were ineffective against gall midge except chlorpyriphos, which exhibited moderate efficacy at 

500 g a.i./ha. This prompted exploring the possibility of other methods of insecticide application like seed 

treatment, seedling root-dip etc. for the management of gall midge, which is cost effective, compared to 

granular insecticides. 

Seed dressing with 16 g of 5% wettable powder of isofenphos / kg of seed after sprouting or soaking 

sprouted seed in a 5% wettable powder or emulsifiable concentrate of isofenphos controlled gall midge 

infestation for about 30 days ensuring the protection for the entire nursery period (Kalode et. al. 1982a). 

Carbofuran at the same rate and method showed moderate effectiveness for 15 days. When sprouted 

seeds were soaked for 3 hrs in either WP or EC formulations (0.5% emulsions) of isofenphos or 

chlorpyriphos for 3 hours, gall midge infestation was checked for 30 days. However, carbofuran, carbosulfan, 

BPMC and monocrotophos were not effective when treated in this way (Kalode et. al. 1982b). 

36


Seedling root dip in 0.02% emulsions of chlorpyriphos for 12 hours or for 3 hours along with 1% urea 

completely checked gall midge damage for 25 days after transplanting. To evaluate the effectiveness of 

different granular insecticides against different ages of gall midge maggots present inside the stem, the 

studies revealed that carbofuran, mephosfolan and isofenphos @ 2 kg a.i./ha basis could check 7 day old 

maggots and prevented gall formation. Chlorfenvinphos, isoprocarb and phorate @ 2 kg a.i./ha checked 

the formation of silver shoots when applied 3 days after larval entry. Insecticides applied 8 days or later 

could not prevent silver shoot formation (Kalode et. al. 1982b). 

Shukla and Kaushik (1983) confirmed the effectiveness of chlorpyriphos and carbofuran granules through 

field studies. While Srinivas and Madhumathi (2004) confirmed the continued efficacy of carbofuran 

against gall midge. 

B. INSECTICDE EVALUATION AGAINST MINOR PESTS IN RICE 

i) Rice skipper, Palopidas mathias (Fabricius) 

Among the insecticides evaluated under field conditions, quinalphos (0.08%) was the best treatment and 

caused 100% mortality with in 2 days after application in Maharashtra, India. Other insecticides tested 

were carbaryl (0.1%), HCH (0.2%), phenthoate (0.08%), phosalone (0.04%) and endosulfan (0.06%) 

(Gaikwad and Dalvi, 1987). 

ii) Blue Beetle, Leptispa pygmaea Baly 

The efficacy of acephate, dimethoate, methomyl, monocrotophos, HCH, carbaryl, permethrin, phosalone, 

BPMC and endosulfan were field evaluated and found to be almost equally effective against the rice blue 

beetle in Maharashtra, India (Dalvi et. al. 1985). 

iii) Root Weevil Echinocneumus oryzae Mshl 

Among the 5 insecticides evaluated in U.P., chlorfenvinphos was the best one (Srivastava et. al. 1976). 

Singh and Dhaliwal (1981) tested 8 granular formulations by broadcasting and observed best reduction 

in larval population’s upto 20 days after application of carbofuran (89.6%), quinalphos (84.9%) and 

phorate (81.25%). Other insecticides like isofenphos, disulfoton and lindane were less effective. Kushwaha 

et. al. (1983) also observed carbofuran granules as the best treatment against root weevil in Haryana. 

iv) Rice thrips Stenchaetothrips biformis Bagnall 

Sathiayanandam et. al. (1987) observed that seed treatment with carbosulfan @ 0.5 g a.i./100g seed 

was the most effective followed by broadcasting of carbofuran granules @ 1.5 kg a.i./ha of nursery. 

Barwal and Rao (1983) recorded highest mortality of thrips in nursery plots treated with quinalphos, 

phosalone and carbaryl in Imphal valley of Manipur. Among the synthetic pyrethroids tested in nursery, 

deltamethrin, flucythrinate, cypermethrin and fenvalerate (0.0015-0.0125%) were as effective as 

37


monocrotophos (0.025%) in Kerala (Reghunath et al., 1988). Singh et al,. (1983) evaluated 10 spray 

formulations @ 500 g a.i./ha and observed highest reduction in number of thrips in plots treated with 

demeton-o-methyl, quinalphos, fenthion, fenitrothion, monocrotophos, endosulfan and phosphamidon 

(90-96%). Chlorpyriphos @ 500 g a.i./ha was also observed to significantly reduce thrips population in 

transplanted rice at 3 days after spraying (Murugesan et. al. 1987). Dimethoate, monocrotophos and 

methamidophos were proved to be effective against thrips in Karnataka, India reducing 98.2 - 99.0% of 

the population after 7 days (Gubbaiah et. al. 1988). In rainfed lowlands, carbofuran alone or in combination 

with quinalphos spray effectively checked thrips population (Panda and Shi 1988). 

v) Gundhi Bugs Leptocorisa oratorius (Fabricius) and Leptocorisa acuta (Thunberg) 

Among the insecticides evaluated malathion was the most toxic followed by formothion, fenthion, 

phosphamidon, fenitrothion and monocrotophos (Krishna Kumar and Visalakshi 1989). Even among the 

dust formulations, malathion dust @ 1.0 kg a.i./ha was the most effective followed by carbaryl and endosulfan 

(Pangtey 1985). However, in a detailed greenhouse study involving 12 insecticides in Orissa, India, Jena 

et. al. (1990) observed that ethofenprox, monocrotophos and oxydemeton methyl @ 500 g a.i../ha 

checked the pest through out the milky stage while malathion, BPMC, quinalphos and chlorpyriphos were 

persistent for lesser period. Combination products involving acephate 45% + cypermethrin 5% @ 500 g 

a.i./ha, beta cyfluthrin 12.5 g a.i./ha + chlorpyriphos 250 g a.i./ha @ 262.5 g a.i./ha were also observed 

to be effective under field conditions (Dhingra et. al. 2003). 

It is advantageous to have ovicidal effectiveness along with toxicity to mobile stages for realizing maximum 

effectiveness of the insecticide against a given pest species. Among the eight insecticides tested by 

Rajendran and Chelliah (1987) against the eggs of L. oratorius, fenthion at an equivalent of 500 g a.i./ha 

was the best followed by chlorpyriphos and phosphamidon. Heinrichs et. al.(1982) at IRRI, Philippines 

tested spray formulations of insecticides by applying to the panicles and confining 2 days old L. oratorius 

adults for 48 hours. The treatments that afforded effective control of gundhi bug were monocrotophos 

(0.05%), chlorpyriphos, (0.16%), phosphamidon (0.07%), acephate (0.09 %) and triazophos (0.07%), 

fenitrothion (0.05%) and carbaryl (0.12 %). 

vi) Rice mealy bug Brevernia rehi (Lindinger) 

A pot culture study in Tamil Nadu, India, revealed that dimethoate and fenthion as sprays were the most 

effective against the nymphs and adults of the mealy bug based on the number of live and dead insects 

at 1-14 days after application (Radja et. al. 1988). Among 11 insecticides evaluated for ovicidal action 

against this pest, fenobucarb @ 250 g a.i./ha equivalent was the best by causing 88% mortality of the 

crawlers that hatched (Gopalan et al., 1987). 

vii) Rice case worm Nymphula depunctalis (Guenee) 

Gagav and Patel (1973) observed that among the 10 insecticides evaluated in the laboratory, fenitrothion 

38


(0.5%), quinalphos (0.025%), carbaryl (0.1%) and monocrotophos (0.048%) were effective. Among 

the synthetic pyrethroids, fenvalerate (100 g a.i./ha) was the most effective compared to cypermethrin 

and deltamethrin under field conditions (Suresh et al., 1985) in Tamil Nadu, India. 

Bandong and Litsinger (1981 a, b and c) at IRRI evaluated 11 insecticides as sprays applied to foliage in 

field conditions and observed that azinphos-ethyl, triazophos, malathion, isoprocarb, chlorpyriphos, carbaryl, 

BPMC and phosphamidon @ 750 g a.i./ha significantly reduced the number of cut leaves compared to 

untreated control. Among the 9 insecticides tested for their ovicidal action, isoprocarb (MIPC), diazinon, 

triazophos and BPMC exhibited better ovicidal action. 

viii) Rice water weevil Lissorhoptrus brevirostris and L. Oryzophilus Kuschel 

Seed dressing of rice with furathiocarb @ 5 or 6 g/kg seed was found effective in Cuba (Neyra et. al. 

1997). In Brazil, pre and post flooding applications of deltamethrin or Lambda cyhalothrin @ 7.5 to 10 g 

a.i./ha were repoted to be effective (Martin’s JF – da, 1997). Carbofuran @ 550 to 750 g a.i./ha applied 

when the pest population started to increase at the permanent flooding stage of rice crop gave effective 

control of these curculionids in Cuba (Meneseses et. al. 1988). Among the other insecticides, Lambda 

cyhalothrin was found to be alternative to carbofuran in Louisiana, US. However, diflubenzuron (280 g 

a.i./ha) was ineffective (Smith et. al. 1985). Novel studies of spot application of synthetic pyrethroids, 

granules of cycloprothrin 2% and ethofenprox (4% oil) could effectively check water weevil, L. oryzophilus. 

Usually, L. oryzophilus inhabit the peripheral zone of rice field during the initial infestation period and 

oviposit in the peripheral areas of the field. By applying these granular insecticides only to the peripheries 

costed only 10% of the conventional broadcast or submerged application of these insecticides in the 

entire field. 

ix) Cut worms Spodoptera frugiperda (J.E.Smith) and Army worms Mythimna separata (Walker) 

Of the 26 insecticides evaluated for their contact toxicity against the armyworm Mythimna separata, 17 

insecticides caused 100% mortality in contact toxicity tests. Cypermethrin, a synthetic pyrethroid killed 

the pest and also prevented larvae from feeding (Basilio and Mochida 1985). In Brazil, diflubenzuron @ 

100 g a.i./ha, monocrotophos @ 240 g a.i./ha, permethrin @ 30 g a.i./ha and fenvalerate @ 25 g a.i./ha 

were effective against S. frugiperda. Fenvelarate was more effective compared to other synthetic pyrethroids 

against M. separata in UP, India (Pande & Tiwari 1999). Earlier studies indicated that chlorpyriphos @ 

400 g a.i./ha (Rizvi and Singh 1981); monocrotophos and quinalphos @ 500 g a.i./ha were also effective 

against M. separata larva under field conditions in Punjab (Dhaliwal and Singh 1986b). Jena et. al. 

(1989) from Cuttack identified carbosulfan as effective insecticide against ear cutting M. venalba. Hiremath 

et. al. (1992) from Dharwad, Karnataka, India, evaluated a poison bait technique in the field traps. The 

bait containing monocrotohos (250 ml monocrotophos 36 WSC+ 50 kg rice or wheat bran + 1 kg jaggery 

+ 68 litres of water) was superior to spray applications of monocrotophos and other insecticides in the 

control of M. separata in sorghum. This technique can also be tried in rice in future. 

39


C. Factors influencing efficacy of insecticides 

i) Compatibility of insecticides and fungicides 

Many a times, both insect pests and diseases occur together in rice. Under such situations, it is easy, 

economical and practicable to use the combinations of suitable insecticides and fungicides in the same 

spray tank. But at the same time, the effectiveness of the individual components in the mixture should not 

be reduced. Therefore, it is essential to evaluate the physical compatibility as well as compatibility with 

regard to bioeffectiveness against insect pests and diseases. 

Usually, BPH and WBPH are associated with the sheath blight disease caused by Rhizactonia solani. 

Sometimes it is the lepidopteran pests like stem borer and leaf folder, which are associated with the blast 

disease particularly in hilly terrains and some hot spot locations for blast like Cuttack of Orissa and 

Nellore of Andhra Pradesh. Therefore, systematic efforts have been put to evaluate the compatibility of 

recommended insecticides and fungicides in Lead Research at DRR and also Coordinated Program of 

DRR. Krishnaiah and Reddy (1992) observed that the combinations of the insecticides carbaryl and 

ethofenprox (at recommended doses against BPH) and fungicides carbendazim and thio-phanate methyl 

(at recommended doses against sheath blight) were compatible in all insecticide-fungicide combinations 

both physically as well as biologically. Peter et. al. (1989) from Tamil Nadu also observed that ethofenprox 

was compatible with fungicides viz., edifenphos and mancozeb. Reddy and Krishnaiah (1997) in their 

continued efforts in this direction found that the insect growth regulator buprofezin (0.02%) was compatible 

with the three fungicides viz., captafol (0.16%), IBP (Iprobenphos) (0.048%) and edifenphos (0.05%) in 

all insecticide fungicide combinations against brown planthopper and sheath blight under glass house 

conditions. Dodan et. al. (1997) from Kaul, Haryana, studied the compatibility of carbendazim and 

edifenphos (the fungicides), monocrotophos and phosphamidon (insecticides) at different dosages and 

observed their compatibility as reflected by their effectiveness against stem borer and neck blast under 

field conditions. They realized higher grain yields in combination treatments compared to either insecticide 

or fungicide treatments alone. Bhaskaran et. al. (1976) observed that combination of phasalone 

(insecticide) and edifenphos (fungicide) gave the best control of leaf folder, green leafhopper and 

Helminthosporium leaf spot disease. 

Similar attempts were also made in other countries like Korea (Song et. al. 1985 and 1987). The insecticides 

BPMC and fenthion and the fungicides isoprothiolane and edifenphos were combined in the spray tank at 

different dosages and observed that the mixtures were more stable than the individual components and 

were also most efficient for simultaneous control of BPH and rice blast. Song et al (1987) reported that 

the combinations of pencycuron and isoprocarb exhibited very high synergism against sheath blight and 

brown planthopper. 

ii) Environmental factors 

Spray formulations 

Rainfall 

Insecticides are applied to rice crop as foliar sprays by mixing with water. However, the quantity of water 

40


required for preparation of spray fluid depends on the type of sprayer used. For applying with mist blower 

or power sprayer the spray fluid normally required in rice is about 100 to 150 litres per hectare. However, 

for hand compression sprayer or the simple knap-sack sprayer, the spray fluid required per hectare is 

400 to 600 litres per hectare depending on the plant stage. The insecticides in recommended dosages 

are mixed separately in a container before loading into the sprayer. 

The insecticide sprayed on the foliage is subjected to several environmental factors. The most common 

environmental factors that affect the spray deposits on rice foliage and their biological efficacy against the 

pests is rainfall. A study has been initiated to know the influence of simulated rainfall on biological 

effectiveness of spray deposits of monocrotophos (0.05%) and carbaryl (0.05%) mainly to estimate the 

time interval required between the spray application and natural rainfall under field conditions. The results 

revealed that 24 hours gap between spray application and the rainfall is required to retain sufficient 

spray deposit of carbaryl and monocrotophos to exert biological effectiveness against BPH N. lugens and 

green leafhopper Nephotettix virescens. (Krishnaiah and Kalode 1988a). If rainfall occurs within the 

same day, it is advisable to repeat the spray. 

Granular formulations 

Temperature 

To estimate the influence of ambient temperature on the biological effectiveness of granules against 

BPH, bioassay studies have been carried out after application of insecticides in both summer season 

(April-May) and winter season (December-January). The results revealed that majority of the insecticides 

exhibited higher toxicity in winter than in summer. Among the seven granular formulations tested, during 

both summer and winter, carbofuran and BPMC were most effective against BPH (Krishnaiah and Kalode, 

1988a&b). 

Water depth 

Water depth in the field is another important factor that influences the bioeffectiveness of granular 

insecticides. Therefore, a greenhouse study involving four water depths viz., saturation, 2.5 cm, 7.5 cm, 

15 cm were evaluated for their influence on the effectiveness of carbofuran to BPH under controlled 

greenhouse conditions. The results clearly showed that increasing water depth beyond 7.5 cm drastically 

reduced the initial and persistent toxicity of carbofuran to BPH at 1 kg a.i./ha. It was also clear that 

saturation was more effective condition for realizing greater toxicity of carbofuran to BPH as compare to 

2.5 cm water depth. This suggests that draining of water in the field infested with BPH recommended for 

reducing the multiplication rate of BPH in endemic areas can be followed advantageously by applying 

granular insecticides immediately after field is drained and comes to saturation level (Krishnaiah and 

Kalode 1988a). 

iii) Soil factors influencing toxicity of granular insecticides 

Persistent toxicity of granular insecticides carbofuran and phorate against BPH nymphs in soils with 

41


varying physioco-chemical properties have been investigated to make appropriate recommendations in 

selecting a suitable insecticide in a given soil type (Krishnaiah and Kalode 1992a). Four types of soils viz., 

red sandy, sandy loam, clay and sandy clay loam with P H ranging from 6.5 to 9.2 and EC (ds/m) varying 

from 0.03 to 0.67 were stabilized under greenhouse conditions in pots and the rice plants were grown 

upto 45 days. Carbofuran was applied @ 2 kg a.i./ha and phorate @ 3 kg a.i/ha by two methods of 

application viz., broadcasting in standing water and soil incorporation. Persistent toxicity to BPH nymphs 

was assessed. The results clearly showed that with increase in P H and EC of the soil, the persistent toxicity 

(PT) of carbofuran was drastically reduced from 1228 to 655, while PT of phorate was not altered that 

much (PT was 1421 in red sandy soil with 6.5 P H and 1318 in alkaline sandy clay loam soil with a P H of 

9.2). This showed that in alkaline soils phorate should be preferred over carbofuran for the management 

of brown planthopper (Table 6). Sridevi et. al. (1995) from APAU, Rajendranagar, in a similar study 

observed that more than 50% of BPH mortality was recorded in soils with low P H compared to negligible 

mortality in alkaline soils with high P H by carbofuran granules. 

42 

Table 6 : Effect of soil types on persistent toxicity (PT) of granular insecticides 

against brown planthopper 

Soil type P 

Red Sandy 6.5 0.03 895 de 1228 c 1421 abc 

Sandy loam 7.8 0.13 910 de 1687 a 1502 ab 

Clay 8.7 0.45 565 g 752 ef 968 d 

Sandy clay loam (alkaline) 9.2 0.67 455 h 655 fg 1318 bc 

H EC 

(ds/m) 

PT Value 

Carbofuran (2 kg a.i. /ha) 

Phorate 

(3 kg a.i. /ha) 

BSW – Broadcast in standing water INC – Incorporated in top 1.5 cm soil layer 

(Krishnaiah and Kalode 1992a)


METHODS AND TIMING OF INSECTICIDE 

APPLICATION IN RICE 

Insecticides need to be applied to the rice from nursery to harvest to safe guard the crop from insect 

pests. Apart from potential toxicity of an insecticide to a given pest species or group of pests, the method 

and timing of insecticide application to a great deal influence the realized effectiveness of the insecticide 

against the pest(s). Seed treatment, seedling root dip, root zone application, controlled droplet application 

are some of the methods of insecticide application, which are more unique to rice crop. Further, the 

timing of insecticide application, which depends on nature and mode of action of the insecticide, is very 

important in the management of planthoppers in rice. Hence, a detailed account of all these aspects is 

presented here. 

Seedling root dip method 

In traditional Rice cultivation, growing seedlings in nursery in a small area, pulling them and transplanting 

in the main field is followed. This offers an opportunity to treat the seedlings with insecticides to suppress 

the insect populations during early stages after transplanting. This is economical, effective and ecologically 

sound. 

Seedling dip can be done by two ways: 1) dipping the whole seedlings for a shorter period of 2 minutes 

in insecticide emulsion or suspension 2) dipping the roots of seedlings for longer period, usually 12 hours 

before transplanting. The second method is ecologically safer as the insecticide is confined to root portion 

and thus the predators of pests, which are usually present on the foliage, are not harmed. 

Dipping the whole seedlings in 0.05% insecticide emulsions of chlorpyriphos, monocrotophos, quinalphos 

or phosalone has been attempted in a limited way and found to be successful against stem borers and 

whorl maggot upto about 20 days after transplanting. Although this method is economical over spraying 

the crop immediately after transplanting for the early stage pests like stem borer and whorl maggot, this 

was not effective against gall midge. Further, this is not ecologically safe either to the ecosystem or the 

workers involved in the operation. Hence, the whole seedling dip did not find favour with the rice 

entomologists for large scale testing. The more suitable alternative of seedling root dip or seedling root 

soaking method has gained prominence. The basic procedure for seedling root dip is described below. 

PROCEDURE FOR SEEDLING ROOT –DIP 

A smooth area of 10x1 m is bunded strongly on all sides. A polyethylene sheet of 10.5 x1.5 m is spread 

over the area touching the soil surface and extended along the bunds upto a height of 10-15 cm. The 

water is let in up to a depth of 2 cm and 200 ml of chlorpryriphos is added and mixed thoroughly. 

Uprooted rice seedlings required to plant one acre area are closely arranged within the polyethylene lined 

area immersing roots in insecticide emulsion (0.02%). All these operations are done towards evening 

43


and seedlings are allowed to remain in the insecticide emulsion over night (approximately 12 hours) and 

are transplanted next day morning. 

In case of time shortage, one percent urea can be added to insecticide emulsion in bunded area and 

mixed thoroughly. Roots of seedlings can be dipped in this emulsion for 3 hours and planted. 

By following the procedure, as many as 30 insecticide formulations have been evaluated over a period of 

15 years in coordinated programme as well as in lead research at DRR. Among all the insecticides, 

chlorpyriphos gave consistently good performance against stem borer, gall midge and whorl maggot. 

Even the so-called systemic insecticides like monocrotophos, dicrotophos, phosphamidon and dimethoate 

tried in this method failed to check the infestations of SB, GM and WM. 

Later, it was expressed that 12 hours dipping is too long a period, and several attempts were made by 

mixing various materials along with insecticide emulsions to reduce the dipping period. Of all the efforts, 

1% urea along with insecticide emulsion with dipping period of three hours was found to give effectiveness 

similar to 12 hours dipping with out urea (DRR 1970 to 1985). 

During this period, another organophosphorus insecticide isofenphos was also found to be effective at 

the same concentration as chlorpyriphos (Natarajan and Chandy, 1979; Kalode et al., 1980). Later several 

workers from CRRI, Cuttack and other institutions also confirmed these results (Rajamani et al., 1981 and 

1985; Misra et al., 1981). 

However, chlorpyriphos was not effective against other pests like, green leafhopper, which is also serious 

at times in tungro endemic areas. Therefore, intensive investigations were carried out at DRR under 

controlled greenhouse conditions to identify the most suitable insecticide for the purpose and its effective 

dosage or concentrations. Of the several insecticides tested for the purpose, carbosulfan at 0.02% was 

the best insecticide (Krishnaiah and Kalode, 1986) (Table 7). Therefore, attempts were made to see the 

effectiveness of the combination of chlorpyriphos and carbosulfan (0.01%+0.01%) as seedling root dip 

and was found effective against both gall midge and GLH. 

Table 7 : Effectiveness of carbosulfan as seedling root dip treatment against green leafhopper 

under greenhouse conditions 

Insecticide 

Carbosulfan 0.02 100a 100a 100a 1733a 

Carbosulfan 0.01 100a 80a 60b 945b 

Carbosulfan 0.005 100a 53b 33cd 555c 

44 

Concentration 

(%) 

% mortality at days after treatment PT value* 

1 2 3 

(Krishnaiah and Kalode, 1986)


However, among other insecticides, thiocyclam hydrogen oxalate was also effective against stem borer 

under field conditions but ineffective against gall midge. (Rajamani et al., 1984). Mayabini Jena (2004) in 

her recent work observed that seedling root dip with fipronil (0.01%) and carbosulfan (0.02%) was 

effective against YSB under field conditions. 

After 1990, there were many practical difficulties posed by researchers and farmers for implementing 

seedling root dip in a large scale under farmers’ conditions. These include toxicity caused to the labour 

while carrying insecticide treated seedlings from nursery to the main field, contamination to the labour 

while transplanting etc. Therefore, an alternative strategy has been thought and implemented through 

coordinated programme. That is by applying granular insecticides like carbofuran, cartap, quinalphos and 

isazophos to the nursery 5 days before pulling the seedlings followed by pulling and transplanting as per 

schedule. This allows the insecticides to enter the seedlings and is carried to the main field. The results 

showed that almost all granular insecticides were moderately effective against early infestations of stem 

borer and gall midge but inferior to the seedling root dip with chlorpyriphos which was the check in the 

trial but clearly superior to untreated control with out any insecticide treatment. (Table 8). 

Table 8 : Influence of late nursery applications with granules on pests in early stages 

after transplanting in main field 

Rate 

Application Stem Borer (% dead hearts) 

Gall midge 

(% SS) 

Insecticide (kg a.i/ha)/ 

Conc. (%) 

Time Method RGL WGL RNR FZB Warangal Ragolu 

30 DAT 30 DAT 30 DAT 40 DAT 30 DAT 30 DAT 

Carbofuran 3G 1.5 5 DBP BSW 3.8 3.3 3.3 0.9 0.3 15.1 

Quinalphos 5G 1.5 5 DBP BSW - 5.2 - - 0.9 - 

Cartap 4G 1.5 5 DBP BSW 4.4 1.7 4.3 1.3 0.0 15.6 

Isazophos 3G 2.0 5 DBP BSW 3.8 3.0 2.6 0.6 0.0 15.5 

Isazophos 3G 1.5 5 DBP BSW 4.4 2.5 2.6 1.0 0.1 16.3 

Chlorpyriphos 20EC 0.02% 12 hrs SRD 3.3 0.4 0.9 0.4 0.1 7.4 

Untreated control - - - 6.3 10.1 4.1 5.1 4.9 23.4 

DBP = Days before pulling, BSW = Broadcasting in standing water, SRD = Seedling root dip, 

DAT= Days after transplanting 

(DRR, 1995) 

Root-Zone Application of Insecticides in Rice Ecosystem 

Rice offers unique ecological conditions in the root zone of the plants compared to other irrigated dry 

crops including wheat, maize, sorghum, bajra etc. In an irrigated rice crop, the root system is present in 

45


anaerobic conditions after the oxygen is depleted. The PH of the soil shows a tendency to reach the near 

neutral, although may not exactly be neutral. The anaerobic bacteria and other microbes take the position 

of aerobic bacteria and other organisms present under aerobically grown crops. 

Under these conditions if insecticide or urea fertilizer is placed in the root zone of rice plants, these are 

not subjected to oxidation which usually renders them to rapid degradation. Instead, these remain in the 

same state for longer period. These chemicals are also near the root system, and hence are more easily 

absorbed into the plant. The chemicals are not subjected to losses through volatilization, and leaching. 

Therefore, several attempts were made to develop practical methods of placing the insecticides in the 

root zone of rice plants. Pathak et. al. (1974) at IRRI took initiative in this line of work. Forty one 

insecticides were evaluated under greenhouse conditions as granules, tablets or capsules placed at a 

depth of 2.5 cm at a rate equivalent of 2 kg a.i./ha in the root zone of potted rice plants by using 

Nephotettix virescens, Nilaparvata lugens and Chilo suppressalis as test insects. In their initial evaluation, 

about 25 compounds were effective against N. virescens, while a lesser number exhibited good efficacy 

against N. lugens and C. suppressalis. In further field trials, it was observed that a single application of 

carbofuran, cartap or chlordimeform even at 0.5 kg a.i./ha controlled the insect pests equal to 3-4 

applications of the same insecticides in the standing water. 

Encouraged by these results, attempts were initiated at DRR (formerly AICRIP) where several insecticides 

were tested by root-zone application method both in lead research and coordination (AICRIP 1977-80). 

Similar attempts were also made in other countries like Indonesia (Shagir and Van, 1976), Korea (Choi et 

al., 1977), India (Krishnaiah et. al, 1988b; Reddy and Krishnaiah, 1993) and China (Chiu et. al, 1980). 

In the beginning, the insecticide granules were mixed in a suitable soil, and mud balls were prepared and 

these mud-balls were placed in the root zone @ 1 for each hill or 1 for 2 or 4 hills. However, this method 

was laborious, time consuming and many a situations uneconomical. 

LIQUID INJECTORS FOR ROOT ZONE PLACEMENT 

Liquid injector 

46 

As an alternative, mixing the insecticides in water and injecting the emulsions 

or solutions into the root zone was preferred. This necessitated the development 

of machines to inject the liquid into the root zone. Many types of injecting 

machines were developed and tested at IRRI. Reddy (1989) designed, developed 

and tested a simple liquid injecting device for the purpose. This consisted of 

attaching a lance with 4 delivery points suitable for injecting the liquid into a 

depth of 2.5 cm in the root zone to the ordinary hand compression sprayer. 

First the liquid is placed in the sprayer tank and held at suitable pressure. The 

operator can carry the spray tank with modified attachment; place the injecting 

points in the soil in such a way that it covers eight rows at a time. Then the 

liquid is released for few seconds, which enable the insecticide solution/emulsion 

to be placed in the root zone. The lance is lifted and placed for the next set of

Liquid injector in action 


injections in a forward position. Thus the operator can continuously 

move forward. This is easy economical and practicable. Further 

urea alone or in combination with carbofuran can be placed in 

the root zone by this simple device. Another advantage with this 

applicator is that it is feasible to apply the insecticide even in 

randomly planted crop, which is the most common practice among 

farmers in many areas. 

ROOT ZONE PLACEMENT OF INSECTICIDES AS COATINGS ON UREA SUPER GRANULES 

Root zone placement of urea super granules as a fertilizer conserving method has been attempted for a 

long time. A single application of urea super granules in the root zone at the time of planting or 5 days 

later was an efficient method resulting in season long supply of nitrogen to the crop. By taking this as a 

lead idea, attempts were made to coat carbofuran WP on urea super granules with either coal-tar or neem 

oil and placed in the root zone to enable root zone placement of both urea and insecticide simultaneously. 

(Krishnaiah et al., 1988). The results for 2 seasons clearly showed that single root zone placement with 

insecticide coated super granules resulted in an effect similar to that with 3 broadcast applications of 

carbofuran granules against stem borers, gall midge, whorl maggot and case worm. Comparative studies 

with MIPC, UC-54229, carbofuran, carbosulfan and carbaryl suggested that carbofuran was the best 

insecticide followed by carbosulfan. This method was useful for simultaneous placement of urea also in 

the root zone. Hence it is economical and labour saving technique. 

Nursery protection with insecticides 

Insect pests such as stem borer, gall midge, thrips, hispa etc start attacking the crop right from nursery. 

If these pests are checked right in nursery stage their carry over to the main field is greatly minimized. 

Seed treatment with suitable insecticide(s) before sowing and application of granules or sprays after 

sowing and nursery establishment are the two major methods for nursery protection. 

SEED TREATMENT 

Treating the unsprouted seed with insecticide wettable powders and sowing did not give encouraging 

results for the control of gall midge. Hence, sprouted seed was coated with wettable powders of insecticides 

@ 16 g a.i./kg of the seed and evaluated for their effectiveness against gall midge. Isofenphos gave 

complete control of gall midge through out the nursery period and the effectiveness has extended even 

in transplanted crop indicating high degree of persistence of isofenphos in rice plant. Soaking the sprouted 

seed in 0.2% suspensions or emulsions of isofenphos or chlorpyriphos for 3 hrs prior to sowing also 

effectively checked gall midge for 30 days after sowing (Krishnaiah and Kalode 1983). Shi et. al. (2001) 

observed that mixing 1kg of dry seed with 12-20 g of carbosulfan 35 DC gave significant control of thrips 

(Stenchaetothrips biformis) upto 24 days after sowing. 

47


NURSERY TREATMENT WITH GRANULES OR SPRAYS 

Application of granular insecticides like carbofuran or cartap @ 2.0 kg a.i./ha of nursery at 15 days after 

sowing is normally sufficient to take care of all the major pests like stem borer, thrips and gall midge 

throughout the nursery period. However, if gall midge is the major problem, then carbofuran is preferable 

over cartap. 

Methods and timing of insecticide application for BPH management 

As BPH confines to basal portion of the rice plant, it is obvious that the spray application of insecticides 

should be directed towards basal portion instead of upper foliage. This fact was recognized since 1975 

(Aquino and Heinrichs 1980). Liu (1979) also observed that sprays applied to stems from either a hand 

operated knapsack sprayer or a mobile type high pressure mist blower with multiple hand nozzles were 

7-40% more efficient than the sprays applied to the leaf canopy. There were attempts to utilize other 

methods that can selectively take more proportion of the applied insecticide to the base of the plant. 

Broadcasting granules in standing water was not as effective as broadcasting on soil just kept at saturation 

(Liu and Chang 1984). Low drift micro granules of BPMC were found to be more effective than traditional 

dust application with power duster (Oh et al., 1987). 

Salam et. al. (1986) from India reported that the field effectiveness of polyethylene based and encapsulated 

formulations of carbofuran granules was better than non-encapsulated carbofuran granules. 

CONTROLLED DROPLET APPLICATION OF INSECTICIDES AGAINST BPH 

Pickin et. al. (1981) observed that controlled droplet application (c.d.a) technique with an optimum 

droplet size of 127 milli microns was superior to conventional knapsack spraying. This c.d.a. technique 

gave predicted 30-40% reduction in applied dosage when sprayed on the canopy, but no reduction was 

predicted for applications against the planthoppers which feed at the basal portion of the plants. 

TIMING OF INSECTICIDE APPLICATION IN BPH MANAGEMENT 

Brown planthopper starts appearing in rice crop about 15 to 20 days after transplanting. However, the 

population will be very sparse, i.e. 2 to 5 adults for 100 hills. Within 20 to 25 days the insect will complete 

one life cycle and multiply approximately 25-50 times and spread to neighbouring hills. At this stage, on 

an average one or two adults per hill can be seen. In the next generation, these will multiply and give rise 

to 10 to 40 insects per hill. Continuation of this condition will lead to further build up resulting in 100 to 

1000 insects per hill and often causing hopper burn. By that time, the crop will reach flowering stage. 

Thus, there are undulating population levels of BPH with ascending trend during the crop growth period. 

A critical analysis of the population structure over the entire period starting from the completion of the 

first generation upto the period of peak population, approximately 80 to 90% of the population will be in 

nymphal stage. Hence, the timing of insecticide application is very important and critical for the management 

48


of BPH under practical conditions. Nagata et. al. (1973) made an attempt to determine the optimum time 

of treatment with fine granules of MIPC. These were applied at four times viz. 1. beginning of the third 

generation, 2. peak of the third generation, 3. end of the third generation and 4. beginning of fourth 

generation. Treatment at the beginning of third generation or fourth generation gave better results 

compared to the peak or end of the third generation. Thus, for carbamates or organophosphates, which 

are effective against adults and nymphs, application at the beginning of nymphal emergence is more 

effective as both adults and nymphs are killed. It also takes care of further emerging nymphs after 

application. 

Nagata (1986) continued his studies on optimal timing for application of insecticides. In case of buprofezin 

an insect growth regulator, the optimal timing was found to be mid nymphal stages of the second generation, 

7 to 14 days after the peak emergence of nymphs. On the contrary, applications during early nymphal 

stages were relatively ineffective. As buprofezin is ineffective against adults and kills the nymphs at the 

time of mouting, application at peak nymphal population can wipe out the whole of nymphal population, 

leaving only the surviving adults on the plant which will also eventually die in a short span of time. This 

reveals that the optimum timing for insecticide application for BPH management vary with the type of the 

insecticide and its mode of action. Hirao et. al. (1983) observed that when a mixture containing 1% 

buprofezin and 2% BPMC was applied immediately after the main wave of immigration of BPH, it significantly 

reduced the grassy stunt disease transmitted by BPH compared to later applications. This is understandable 

as the freshly settling BPH in rice fields must be killed before they transmit grassy stunt virus to healthy 

young rice plants. As BPMC is effective against adults and the emerging nymphs are checked by buprofezin, 

this completely suppresses the population build up of BPH and thereby transmission of grassy stunt 

virus. 

CONCLUSIONS 

l For managing insect pests in nursery, soaking sprouted seed in 0.2% chlorpyriphos or isofenphos for 

3 hours before sowing is effective against stem borer, gall midge and whorl maggot through the 

nursery period. 

l Seedling root dip in 0.02% chlorpyriphos for 12 hours can protect rice crop in early stages of 

transplanting. 

l Root-zone placement of carbofuran WP @ 1.0 kg a.i. /ha as coated urea super granules or liquid 

injection of carbofuran + urea with applicators, offers protection equal to 3 granular applications at 

the same dose each time. 

l Timing of insecticide application for BPH management is crucial and depends on type of insecticide. 

For organophosphates and carbamtes, application at the beginning of nymphal emergence is more 

advantageous while for growth regulators like buprofezin application at the time of peak population of 

BPH nymphs is more effective. 

49


SYSTEMIC NATURE OF INSECTICIDES IN RICE: 

THE CONCEPT AND PRACTICE 

Traditional classification of insecticides 

Traditionally insecticides are classified as stomach poisons, contact poisons and systemic insecticides 

based on their nature of entry into the plant system and the insect system. An insecticide when applied on 

the plant continues to remain on the surface where it was applied and when an insect feeds on the treated 

portion of the plant, the poison gets entry into the alimentary canal, absorbed into the haemocoel and 

finally brings about some biochemical change either in the alimentary canal, haemocoel or nervous system, 

thereby, resulting in the death of the insect. Such insecticide is called as stomach poison as it brings 

about death of the insect only after getting entry into the stomach. 

An insecticide is called a contact poison when it is applied to the plant surface, remains on the surface of 

the plant but when an insect comes in touch with the chemical, the insecticide is capable of penetrating 

through the insect cuticle, enter into the haemocoel and then nervous system there by bringing about 

death of the insect by interacting with appropriate physiological loci. 

An insecticide is said to be systemic insecticide when it can penetrate into the plant system, get translocated 

into the plant parts other than those where the insecticide was originally applied. When insects feed either 

on the portion, which was treated or originally untreated, the insecticide enters into the alimentary canal 

of the insect system, then to the haemocoel and finally the nervous system resulting in the death of the 

insect. 

The above traditional classification of insecticides was based on old situation where the inorganic insecticides 

like arsenicals were purely stomach poisons and organic insecticides like nicotinoids and pyrethrins were 

contact poisons. However, after the advent of purely synthetic insecticides starting from organochlorines, 

organophosphates, carbamates, synthetic pyrethroids, and the latest class of neonicotinoids, majority of 

these insecticides can act both as stomach poisons as well as contact poisons. However, all the members 

of these groups are not systemic as far as plant system is concerned. There are systemic insecticides in 

many of these modern groups of insecticides along with others, which are contact insecticides, and only 

a few are stomach poisons. 

Potential toxicity vs. expressed toxicity 

Potential toxicity of an insecticide is the ability to bring about death of an insect at low dosages and in a 

shorter period, when the poison is either applied topically on the insect or given through its food. This 

depends upon the ability of an insecticide to move into the insect system, low rate of degradation of the 

chemical in insect system or high potentiation in the insect system and high affinity of the molecule to the 

specific physiological loci in nervous system, which results in the death of the insect. Generally one, two or 

all these factors may contribute for this potential toxicity of an insecticide towards a pest species. And this 

50


may be the reason why neonicotinoids are extremely effective against planthoppers and leafhoppers and 

almost have no practical toxicity towards lepidopterans. On the other hand, insecticides like flubendiamide, 

spinosad and indoxacarb have excellent toxicity towards lepidopterans and have no practical toxicity to 

homopterans like leaf and plant hoppers. 

The realized toxicity is the ability of an insecticide to effectively check a given pest species under practical 

field conditions. This depends upon not only the potential or innate toxicity but also the method of application, 

the time of application, and other environmental factors, which determine the extent of accessibility of 

the chemical to the insect. This also depends on the position of the insect in the plant, for instance inside 

the stem, or on the leaf sheath and the type of mouthparts and the amount of plant material consumed 

by the insect. For instance monocrotophos has high potential toxicity to leaf hoppers and plant hoppers 

but fails to check them when given as a seedling root dip or when applied to soil as granules. 

Systemic action: differences among various insecticide groups 

The insecticides like carbofuran, MIPC, and BPMC among the carbamates, phorate, disulfoton, fenthion, 

and isazophos among organophosphates are used only as granules applied to standing water on the soil 

surface. These get entry into the plant through root system, move upwards, through xylem into the stem 

and then into the leaves and finally get distributed into other plant cells including phloem. That is why they 

are able to kill even the phloem feeders among the rice pests like BPH and WBPH. 

Other insecticides like quinalphos, ethoprop and chlorpyriphos among organophosphates can be applied 

as granules to the soil but have got limited translocation in the plant system and are probably concentrated 

in the growing portions of the rice plant. Hence, these are effective against internal feeders like stem 

borer, gall midge, and whorl maggot and exert very little influence on leaf feeders like leaf folder and rice 

hispa although they have good potential contact toxicity against these two insect pests when applied as 

foliar sprays. 

In case of cartap and thiocyclam, which are neiristoxins, these have translocation in rice plant reaching 

the leaf even when applied as granules to the soil. This together with their high innate toxicity to leaf 

folders might be contributing for their excellent field effectiveness against leaf folder. 

Monocrotophos: systemic action in rice vs. coconut 

Monocrotophos, which has excellent contact toxicity against leaf- and planthoppers, is generally considered 

to be having systemic action in the plants. However, in case of rice it failed to be translocated into rice 

plant either as a granule or as a seedling root dip treatment as it exercised poor control of stem borer 

and whorl maggot in spite of it’s high innate toxicity to these pests. It also showed no appreciable toxicity 

to plant hoppers and leaf hoppers when given as a seedling rood dip in spite of its high potential contact 

toxicity to leaf and plant hoppers in rice. This reveals that it is not really getting translocated in sufficient 

quantities in the rice plant system and getting distributed into the entire plant system including phloem. In 

contrast, monocrotophos has exercised excellent systemic action and translocation in another 

51


monocotyledonous plant the coconut. In coconut, root feeding with monocrotophos has resulted in excellent 

control of black headed cater pillar, of coconut. This emphasizes the point that an insecticide may not be 

truly systemic in one plant but may exercise true systemic action in another plant owing to the differences 

in the molecular translocation physiology among different plants. 

Chlorpyriphos has limited translocation 

Chlorpyriphos has shown excellent efficacy against stem borer, gall midge and whorl maggot when given 

as a seedling root dip before transplanting of rice plants. It has also shown good control of gall midge in 

the nursery when sprouted seeds of rice were soaked in chlorpyriphos emulsion for 3 hours before 

sowing. However, chlorpyriphos failed to check effectively the leaf feeding insects like leaf folder and rice 

hispa, or the sucking pests like plant hoppers and leafhoppers. This throws the light that chlorpyriphos is 

getting accumulated only in the young growing parts of the plants and thus exercising its effectiveness 

against stem borer, gall midge and whorl maggot whose larvae confine to the growing portions of rice 

plant. 

Carbosulfan: a true systemic insecticide in rice 

When several insecticides including monocrotophos, have been evaluated for their effectiveness as seedling 

root dip treatments against whitebacked planthopper, brown planthopper and green leafhopper, only 

carbosulfan has exercised effective control of all the leaf and plant hoppers. This reveals that carbosulfan 

has excellent translocation in the plant system moving through xylem from lower to upper portions of the 

plant and then disbursing into the phloem through other tissues, which alone can bring about excellent 

control of BPH and WBPH which are purely phloem feeders. High innate toxicity of carbosulfan to leaf and 

planthoppers might be considered as the reason for its effectiveness but monocrotophos in spite of its 

high innate toxicity to BPH and WBPH failed to check leaf and planthoppers as a seedling root dip 

treatment. 

Downward translocation of insecticides in rice 

When we talk of the systemic action in rice plant, it is not merely the upward movement or translocation of 

insecticides when applied either to soil or seedling root dip but, a true systemic insecticide should also 

have downward translocation as well when applied to the upper parts of foliage like leaves. This property 

can be effectively evaluated by spraying the insecticides to the leaves and confining the insects to the 

base of the plant, which is uncontaminated. When several insecticides have been evaluated in this manner 

for their downward translocation property in rice plant, only BPMC could exercise good initial kill of BPH. 

However, the persistence lasted only for five days indicating that a small proportion of BPMC applied to 

the foliage has really been translocated downwards to effectively check BPH. None of the other insecticides 

including monocrotophos, which have high innate toxicity to BPH, could show such a downward translocation 

in rice plant. 

52


When the insecticides like neonicotinoids have been evaluated for downward translocation property in 

rice plant in a similar manner, the insecticides like imidacloprid, thiamethoxam, and clothianidin, which 

have very high potential toxicity against BPH and WBPH, could not kill the insects present at the basal 

uncontaminated portion of the rice plant. This shows that there is no real downward translocation of 

neonicotinoids in the rice plant when applied to the foliage. The extreme effectiveness of neonicotinoids, 

which is realized under field conditions even at a dosage as low as 25 g a.i/ha, might be mainly through 

contact action of these neonicotinoids when sprayed on the plant system. 

53


MOLECULAR AND BIOCHEMICAL APPROACHES 

FOR INSECTICIDE UTILIZATION IN RICE 

After the adverse ecological effects associated with chlorinated hydrocarbon insecticides such as 

biomagnification and high level of persistence in the ecosystem were documented and recognized, the 

organophosphates and carbamates were used for rice insect pest management since early seventies. 

However, other problems associated with insecticide use such as toxicity to natural enemies, non-target 

organisms and the operator continue to exist even with OPs and carbamates. The major reason is that the 

biochemical loci in the mode of action of OPs and carbamates are the same in insects and mammals. 

Further, lack of selectivity among different groups of insects is another reason. Hence attention was paid 

by researchers world over to device the insecticides that attack the biochemical loci, which are specific to 

insects and also have reasonable selectivity among different orders of insects. As far as rice is concerned, 

the major lead in this area of research comes from Japanese scientists working in both government and 

private organizations in Japan. 

A wide variety of approaches for this problem have been followed. These include 

1. Identification and isolation of naturally occurring plant lectins and their incorporation in rice through 

molecular approaches 

2. Synthesis of new groups of chemicals on empirical basis and selecting suitable molecules after bioassay, 

utilizing the typical insects of economic importance. 

3. Modifying the structure of the already existing carbamates and OPs and identifying the molecules with 

more selectivity among different insect orders. 

4. Designing new molecules to act as synergists to overcome the problem of insecticide resistance 

5. Synthesising new molecules, which can attack different active sites in the enzymes, like acetyl 

choline-esterases present in insects resistant to OP s and carbamates. 

1. Identification and isolation of naturally occurring plant lectins 

Powell et. al. (1993) in U.K. isolated the lectins viz., Galanthus nivalis agglutinin (GNA), wheat germ 

agglutinin (WGA) and the enzyme soybean lipoxygenase (LPO) and bioassayed on BPH and GLH Nephotettix 

cincticeps after incorporating into artificial diets. These substances at 0.08 to 0.1% exhibited significant 

antimetabolic effects on 1 st and 3 rd instar nymphs of BPH and 3 rd instar nymphs of GLH. Later attempts 

were made to isolate the genes responsible for these lectins and enzymes and incorporate into rice 

(Nagadara et. al. 2003). 

2. Synthesis of new groups of chemicals on empirical basis and selecting suitable molecules 

Kato et. al. (1989a) studied the structure activity relationships of 2-alkyl thio-4-thiazolyl methane sulfonates 

54


and their toxicity to BPH and GLH (N. cincticeps). The branched C3-C4 alkyl thio derivatives and their 

oxidized equivalents were most active against susceptible as well as OP and carbamate resistant GLH. 

Another group of molecules viz., 6-alkylthio-2-pyridyl alkanesulfonates and their sulfoxides and sulfones 

were also observed for their toxicity to the above two species of insects (Kato et al., 1989b). In a series 

of 6-isobutylthio-2-pyridyl alkanesulfonates and their sulfoxides and sulfones, the methane-, ethane-, and 

chloromethane sulfonates showed stronger insecticidal activity than higher alkane sulfonates. Some of 

these were also inhibitory to acetyl cholinesterase from OP resistant strains of GLH. 

Yagi et. al. (1999) observed that 4-tert-butyl-2- (2, 6-dichloro-4-trifluoromethylphenyl)-1,3,4-oxadiazolin- 

5-one gave the highest activity against N. cincticeps among a series of derivatives. Obata et. al. (1992) 

in a similar study observed that N- (3-phenoxybenzyl)-4-pyrimidinamine was effective against BPH. 

PYMETROZINE: A NOVEL CONTACT INSECTICIDE 

Sato et. al. (1996) in Japan, observed excellent control of both BPH and WBPH under field conditions due 

to application of pymetrozine at as low as 63 g a.i./ha. Laboratory studies revealed that paralysis of legs 

of treated insects followed by reduced or complete inhibition of feeding and reproduction in BPH was 

responsible for population reduction in field conditions. In case of WBPH also more or less similar effect 

was observed. 

MUSCARINIC AGONISTS AS INSECTICIDES 

Dick et. al. (1997) from USA reported that the agonists of muscarinic receptor in insects proved to be 

extremely active against N. lugens and N. cincticeps in laboratory bioassays. 

ETHOFENPROX, A NOVEL ETHER DERIVATIVE INSECTICIDE & ITS RELATIVES 

Ethofenprox is very similar in its structure to synthetic pyrethroids but it is proved to be extremely effective 

against planthoppers and leafhoppers in rice. In addition, it has moderate toxicity to Lepidoptera and 

Coleoptera. Ethofenprox proved to be effective against OP and carbamate resistant BPH, WBPH and GLH 

and does not cause resurgence of BPH under field conditions. This molecule has extreme inbuilt safety to 

mammals (Yoshimoto et al., 1989). 

By taking clue about the desirable properties of ethofenprox, another derivative called flufenprox has 

been synthesized and evaluated. This molecule proved to be effective against wide range of pests belonging 

to orders of Lepidoptera and Coleoptera with inbuilt safety to mammals and also fish, earthworms and 

spiders (Gordon et al., 1992). 

Another derivative of ethofenprox, synthesized by replacing quaternary carbon atom with silicon atom 

proved to have broad-spectrum insecticidal activity with extremely low toxicity to fish and mammals. This 

even gives the clue that by substituting carbon atom in insecticide molecules of other groups it can be 

possible to get derivatives, which are safer to environment with less toxicity to fish and mammals (Ohtsuka, 

1993). 

55


INSECT GROWTH REGULATORS 

A new compound (4-chloro-5-(6-chloro-3-pyridylmethoxy)-2-(3,4-dichlorophenyl)-pyridazin-3-(2H)-one) 

was observed to exhibit juvenile hormone activity and inhibited metamorphosis selectively against the 

most important sucking pests like BPH and GLH. Residues of 1mg a.i./l inhibited development. The affected 

insects could not complete their development from one nymph to next nymphal instar or nymph to adult 

and died. The compound was persistent for about 40 days on sprayed rice plants (Miyake et al., 1988). 

DIFLUBENZURON: A SELECTIVE INSECT GROWTH REGULATOR FOR LEPIDOPTERA 

Diflubenzuron inhibits chitin synthesis in immature caterpillars, kills eggs and sterilizes adults. The detailed 

studies on the rice pest S. mauritia by Beevi and Dale (1980 & 1984) in India revealed that early instar 

larvae were more susceptible than late instars. The malformations that occurred in treated larvae were 

inability to moult or partial moulting, reduction of pupal size, larval-pupal intermediates, deformation of 

wings and body of adults when late larvae were treated. When diflubenzuron at 100 to 1000 ppm in 

honey solution was fed to adults of S. mauritia, it resulted in immediate death of some adults, shorter life 

span for all the adults, deposition of fewer eggs, where none hatched. Diflubenzuron even at 10 ppm 

when fed to adults caused 64% sterility of the eggs laid by treated adults. 

With regard to rice leaf folder, C. medinalis, the results were not encouraging. The feeding inhibition of 

larvae was less than 50% even at as high as 500 ppm (Rao et al., 1987). The field observations made by 

the senior author (unpublished) at DRR farm also showed that diflubenzuron was not effective against C. 

medinalis. 

BUPROFEZIN, A CHITIN INHIBITOR AND GROWTH REGULATOR FOR HOMOPTERA 

Buprofezin is an inhibitor of chitin synthesis in insects and also acts as a growth regulator. It was synthesized 

as a chance product of systematic synthesis programme for fungicidal development. The treated immature 

insects are unaffected until the starting of moulting process and the insects fail to shed the exuviae at the 

time of moulting. Buprofezin is specific to homoptera particularly delphacidae and cicadellidae. In adults, 

normal ovarian development was affected and the number of eggs laid was drastically reduced with 

increase in concentration of the insecticide. As it targets the insect specific loci of moulting process, it is 

safe to mammals, fish and also spares predators of homopteran pests like spiders and mirid bugs (Kajihara 

et al., 1982; Heinrichs et al., 1984). Field trials in Japan and other countries showed high reduction of 

BPH populations in buprofezin treated plots. 

Asai et. al. (1983 and 1985) made detailed studies on mode of action of buprofezin in BPH. Apart from 

its known effects on nymphs and adults, the eggs treated in situ by spraying on plants containing eggs at 

250 ppm resulted in 43.3% hatching compared to 100% in untreated check. The life span of treated 

adults was also reduced drastically. 

When 5 th instar nymphs of BPH were treated at 50 ppm of buprofezin with in 1hr of their last moult, the 

treated nymphs began to die after 84 hrs of treatment and none emerged as adults. The histological 

56


observations showed no differences in the cuticle between treated insects and untreated insects upto 72 

hrs after treatment inferring that the time of action of buprofezin is at the time of moulting only (Uchida 

et al., 1985). Further the reduction in oviposition by adults as well as mortality in buprofezin treated 

nymphs could be countered by treatment with the classical moulting hormone, the 20-hydroxy ecdysterone, 

suggesting that buprofezin adversely affects the moulting hormone in treated insects (Uchida et al., 

1986; Kuriyama and Yamaguchi, 2000). 

Bei et. al. (1996) from China reported that buprofezin was not translocated from root to stem but significantly 

translocated from leaves to stem. Buprofezin kills BPH nymphs by contact with dorsal thorax, or tarsus in 

legs or through mouthparts (rostrum). 

DIAPAUSE BREAKING MOLECULES 

Occurrence of diapause or inactive stage in rice stem borers in northern parts of India during winter is 

well known. If we can break diapause earlier than normal time through chemicals, the emerging adults will 

not find host plants i.e. rice and hence die without laying eggs. Chakravorthy et. al. (1985) topically 

treated the field collected diapausing larvae of YSB with juvenile hormone mimics such as hydroprene, 

methoprene and precocene-II (6,7-dimethoxy-2, 2-dimethyl-2H-1-benzpyran) at 10 to 200 micrograms 

per larva and maintained at 23 0 C. The development of larvae was accelerated leading to early emergence 

of adults. 

3. Modifying the structure of already existing carbamates and OPs 

Carbosulfan, a derivative of carbofuran was synthesized in 1982 and widely tested against rice insect 

pests. It is systemic in rice similar to carbofuran, extremely effective against hoppers even as seedling 

root dip method. Unlike carbofuran, which is useful as a soil insecticide, carbosulfan is a good foliage 

insecticide as well as soil insecticide. It has better inbuilt safety to mammals and natural enemies compared 

to carbofuran. It was recommended against hoppers as well as lepidopteran pests in rice (Riddell et al., 

1982; Krishnaiah and Kalode, 1986a). 

Goto et. al. (1988) synthesized a number of new amino-sulfinyl derivatives of carbofuran, linking different 

N-substituted amino acid-esters and its analogs to the carbamyl nitrogen atom of carbofuran through a 

sulfur bridge and evaluated against the rice pest N. cincticeps. Majority of the derivatives showed good 

insecticidal activity against the hopper. Some of them were as effective as carbofuran. 

4. Designing new molecules to act as synergists to overcome the problem of insecticide 

resistance 

The major method of countering the insecticide resistance in insect pests is by utilization of synergists. In 

general synergists block the enzymes responsible for the degradation of the insecticide molecules in the 

resistant strains there by more toxicant will reach the target of action. Some synergists may possess 

slight toxicity to the target pests or may be completely non-toxic by themselves but enhance the toxicity of 

57


the insecticide when used in combination. Konno and Shishido (1990) synthesized one hundred noninsecticidal 

carbamates and evaluated their synergistic activity to fenitrothion and primiphos methyl resistant 

5 th instar larvae of Chilo suppressalis. The N, N-dimethyl carbamates with substituted phenyl and heterocyclic 

groups had synergistic activity to fenitrothion. Among all, 2-dimethylamino-6-methyl-4-pyrimidinylesters 

were extremely synergistic to fenitrothion in resistant C. suppressalis and reduced the resistance level 

from 1202 to 1.1.fold by strong inhibition of fenitroxon detoxification by protein binding and hydrolysis. 

5. Synthesising new molecules, which can attack different active sites in the enzymes, like 

acetyl choline-esterases present in insects resistant to OP s and carbamates : 

N. cincticeps, the most important GLH species in Japan has developed resistance to many OPs and 

carbamates. The main mechanism of resistance was insensitivity of the target site of action, the acetyl 

cholinesterase enzyme (AChE) in nervous system of the insects. Kyomura and Takahashi (1979) attempted 

to develop new carbamate compunds that could control such resistant hoppers. The major aim was to 

increase the interaction between the AChE in resistant strains and the molecules of new insecticides. The 

combination of N-propyl carbamate with N-methyl carbamate with the same or different phenyl group 

resulted in potent synergistic activity and it was exhibited even under field conditions. The biochemical 

evaluation revealed that AChE from resistant leafhoppers had an additional site sensitive to N-propyl 

carbamates that was distinct from N-methyl carbamate sensitive site present in AChE from susceptible 

leafhoppers. A single inhibitor could not inhibit both the sites but when two inhibitors were combined each 

interacted with the preferred site. This appeared to be the rational basis of synergism between N-propyl 

carbamates and N-methyl carbamates. 

58


TOXICITY OF INSECTICIDES TO NATURAL 

ENEMIES IN RICE ECOSYSTEM 

Toxicity of insecticides to natural enemies of planthoppers 

In rice ecosystem, green mirid bug Cyrtorhynus lividipennis, brown mirid bug Tytthus parviceps and velid 

predator or water strider Microvelia douglassii atrolineata and large number of species of spiders constitute 

the natural enemy complex against the leaf and planthoppers viz., brown planthopper, white backed plant 

hopper, and green leafhopper. 

Use of insecticides continues to be one of the major tactics employed by farmers to minimize the yield 

losses in rice from these pests. Conservation of natural enemies is an important component of modern 

integrated pest management (IPM). Pesticides that are not harmful to natural enemies can be effective 

tools for IPM. There are several instances where the use of some insecticide molecules, particularly 

synthetic pyrethroids led to resurgence of N. lugens and S. furcifera resulting in ‘hopper burn’ and 

complete loss of rice crop. Destruction of natural enemies has been observed to be responsible for BPH 

resurgence (Heinrichs et al., 1982; Krishnaiah and Kalode, 1987). 

TOXICITY TO SPIDERS 

Chen and chiu (1979) from China observed that among the three insecticides that were commonly used 

against BPH, viz. acephate, carbofuran and monocrotophos against two species of spiders viz., Oedothorax 

insecticeps and Lycosa pseudoannulata, acephate was found to be relatively safer than the other two 

insecticides against both the species. Later, Kumar and Velusamy (1996) reported that, of the 7 insecticides 

Oxyopes sp. Tetragnatha sp. 

viz., acephate (500g a.i./ha), BPMC (500 g a.i./ha), ethofenprox (50 g a.i./ha), quinalphos (750 g a.i./ 

ha), chlorpyriphos (500 g a.i./ha), monocrotophos (500g a.i./ha) and carbaryl (750 g a.i./ha), acephate, 

BPMC and ethofenprox were less toxic to three species of spiders viz., Lycosa psedoannulata, Tetragnatha 

javanica and Oxyopes javanus. These results were also confirmed by calculating LC 50 values for these 

insecticides. Acephate was also observed to be less toxic to spiders in their later studies (Kumar and 

59


Velusamy 1999 and 2000). Yoo et. al. (1984) from Korea observed that BPMC and MIPC were relatively 

less toxic to spider, Pirata subpiraticus compared to BPH. 

Tanaka et. al. (1990) from Japan reported that among the most commonly occurring spiders in rice 

ecosystem viz., Paradosa pseudoannulata, Ummelliata insecticeps and Gnathonarium exsiccatum, all the 

species were susceptible to ethofenprox, while P. pseudoannulata was more susceptible to phenthoate 

and carbaryl. The other insecticides tested were diazinon and BPMC. The insecticides were tested by 

dipping method to 1st instar spiderlings in the laboratory and the toxicities were expressed based on LC 

50 values. However, the field trials in India and other countries clearly showed that ethofenprox is safer to 

spiders but the dosage required is one tenth of other insecticides. Even, Tanaka. et al., (2000) observed 

that ethofenprox was 35 times less toxic to adult spiders compared to 1st instar spiderlings. 

In field trials, in India, Patel et. al. (2004) observed that endosulfan was relatively safer than other 

insecticides like, dichlorvos, triazophos, cartap, carbofuran, imidacloprid and BPMC. By using dipping 

method against first instars of four species of spiders, viz. Lycosa pseudoannulata, Tetragnatha maxillosa, 

Ummelliata insecticeps and Gnathonarium exsiccatum with nine insecticides, Tanaka et. al. (2000) observed 

that T. maxillosa was the most susceptible species. Raman and Uthamasamy (1983) observed least 

mortality of L.psuedoannulata with carbosulfan (0.04%) by contact toxicity tests on rice seedlings compared 

to fenthion, methamidophos, phosphamidon (all at 0.04%), deltamethrin, fenvalerate and cypermethrin 

(all at 0.002%). Based on field observations, Bhavani and Rao (2005) reported that imidacloprid was 

also safe to spiders. 

BUPROFEZIN, A SELECTIVE INSECTICIDE TO NATURAL ENEMIES OF BPH 

Buprofezin, an insect growth regulator has shown excellent toxicity to BPH and safety to almost all natural 

enemies of the pest viz., Cyrtorhinus lividipennis, and the parasitoids Paracentrobia andoi and 

Haplogonotopus sp. apart from spiders (Kanaoka et. al. 1994; Choi et. al. 1996) 

60 

Haplogonotopus sp.

STUDIES AT DRR 


Continuous programme of evaluating insecticides for their relative toxicity to important natural enemies 

of BPH at DRR under greenhouse conditions showed that acephate (1200 ppm) was least toxic to green 

mirid bug C.lividipennis and brown mirid bug T. parviceps followed by fipronil (100ppm). Both imidacloprid 

and thiamethoxam were relatively more toxic even at 25 to 50 ppm. This was based on confining nymphs 

and adults of these predators to sprayed plants (Jhansi Lakshmi et al., 2001a & b). However, in similar 

studies with velid predator, Microvelia douglasi atrolineata, it was found that fipronil followed by acephate 

were safer than thiamethoxam and imidacloprid (Krishnaiah et al., 2001) (Table 11). 

C. lividipennis T. parviceps Microvelia sp. 

In case of combination products against mirid bugs viz., C. lividipennis and T. parviceps acephate + 

cypermethrin and chlorpyriphos + cypermethrin exhibited less persistent toxicity compared to beta cyfluthrin 

+ chlorpyriphos and imidacloprid + beta cyfluthrin. But all the combination products were more toxic 

than single compound insecticides like acephate and monocrotophos. Similar results were obtained in 

case of velid predator. (Jhansi lakshmi et. al. 2003; 2004 and 2006a) (Table 9). 

In another study on the safety of insecticides to natural enemies, the three combination products viz., 

ethiprole+imidacloprid, thiamethoxam+lambdacyhalothrin and flubendiamide + fipronil were highly toxic 

to all the three natural enemies viz., green mirid bug, brown mirid bug and veliid predator. The single 

compound insecticides viz. ethiprole, spinosad, flubendiamide were less toxic to the veliid predator than 

indoxacarb and check insecticide, acephate. Flubendiamide was least toxic to green mirid bug compared 

to acephate and other insecticides. All the single compound insecticides were toxic to brown mirid bug 

(Jhansi Lakshmi et. al. 2008) (Table 9). 

Among twelve acaricides tested for their safety to three hemipteran predators viz., C. lividipennis, 

T. parviceps and M. douglasi atrolineata, fenpropathrin and diafenthiuron were highly toxic, spiromesifen, 

pyriproxifen, milbemectin and dicofol were less toxic whereas other acaricides such as profenophos, 

ethion, propargite, abamectin and fenazaquin were moderately toxic to these predators (Jhansi lakshmi 

et al., 2006b) (Table 10). 

61


Table 9: Toxicity of selected combination products of insecticides to hopper predators 

(persistent toxicity at 72 h after exposure) 

Treatment Conc. of a.i. 

(ppm) 

Persistent toxicity 

T. parviceps 

M. atrolineata C. lividipennis 

Adults Nymphs 

Chlorpyriphos 50% + 


(Nurelle D 505) 

344 2800 1526 2031 1294 

Betacyfluthrin 12.5g + 

Chlorpyriphos 250g 

(Bulldock star 262.5EC) 

393 2800 1823 2800 2730 

Acephate 45%+ 


(Upacy 50DF) 

500 2758 936 2532 910 

Imidacloprid 50g+ 

Betacyfluthrin 50g 

(Confidar Ultra 100 EC) 

30 2800 2800 2788 2800 

Ethiprole 40% + 

imidacloprid 40% 

100 2800 2800 2800 2716 

Thiamethoxam 12.6% + 

lamdacyhalothrin 9.4 % 

(Alika 247 ZC) 

44 2800 2800 2800 2800 

Flubendiamide 36%+ 

Fipronil 30% 

(50 g product) 

50 567 2723 2800 2800 

Betacyfluthrin 

(Bulldock 25 EC) 

12.5 2800 1733 2772 2436 

Thiacloprid 

(Calypso 240 SC) 

120 2607 2800 2772 1313 

Monocrotophos 

(Nuvacron 36 WSC) 

500 1666 100 511 198 

Acephate 

(Starthene 75 WP) 

750 1382 317 1310 300 

Spinosad 45 SC 56 255 1897 2086 1394 

Flubendiamide 

(Ril 038 20 WDP) 

25 329 48 1958 1598 

Ethiprole 10EC 50 14 1948 2478 986 

Indoxacarb 

(Kingdoxa 14.5 SC) 

29 928 2429 2632 1877 

62 

(Jhansi lakshmi et. al. 2003; 2004, 2006a, 2008)


Table 10 : Relative persistent toxicity of selected acaricides to the predators 

at 72 hours after exposure 

Acaricide 

Conc. of a.i 

(ppm) 

Cyrtorhinus. 

lividipennis 

Tytthus 

parviceps 

Microvelia 

douglassi 

Profenophos (Carina 50EC) 500 403 de 1407c 793de 

Ethion (Fosmite 50 EC) 500 812 c 1918b 927d 

Propargite (Omite 57 EC) 500 371 c 1047cde 732de 

Propargite (Simba 57 EC) 500 353 c 766f 1449c 

Spiromesifen (Oberon 240 SC) 72 476 dc 1323cd 532c 

Fenpropathrin (Meothrin 30 EC) 150 2296a 2800a 2800a 

Milbemectin (Milbeknock 1%) 2.5 392 de 845ef 894d 

Abamectin (Vertimec 1.9 EC) 10 1078bc 1146cde 2205b 

Pyreproxifen (Admiral 10EC) 75 560 d 681def 714de 

Fenazaquin (Magister 10 EC) 125 1162b 1374c 1855b 

Diafenthiuron (Polo 50 WP) 450 2142a 2107b 2800a 

Dicofol (Kelthane 18.5 EC) 500 476 de 1257cd 1260e 

Untreated control 55 f 251g 151f 

Figures in a column followed by the same letter are not significantly different at P=0.05 by DMRT. 

(Jhansi lakshmi et. al. 2006b) 

INSECTICIDAL INFLUENCE ON GALL MIDGE PARASITES 

It is painful to admit that there is very less information available on the effect of insecticide treatments on 

Platygaster oryzae, the larval pupal parasite of rice gall midge. A field observation by Samalo et. al. 

(1983) revealed that seedling root dip with 0.02% chlorpyriphos followed by one application of ethoprophos 

Parasitized gall 

Platygaster sp. 

63


granules 1.0 kg a.i./ha at 30 DAT exhibited very little adverse effect on the P.oryzae at the same time 

maintaining good control of the pest. Patnaik and Sathpathy (1983) observed less adverse effect on 

P.oryzae by granular insecticides like carbofuran, and phorate but the later was preferable based on 

effectiveness on gall midge. 

Although sprays are in general not effective against gall midge, they are inevitable against the pests like 

leaf folder. Hence, studies were conducted to see their toxicity to gall midge parasite P. oryzae. Among the 

sprays, phosalone was the least harmful to the parasitoid, followed by phosphamidon and endosulfan. 

EFFECT ON COCCINELLID PREDATORS IN RICE ECOSYSTEM 

Among the insecticides viz., chlorpyriphos, fenitrothion, formothion, phosphamidon, and quinalphos, tested 

for their toxicity to three coccinellid predators which are commonly found in rice ecosystem viz., Coccinella 

rependa, Micraspis discolor and M.vincta, fenitrothion was least toxic to C. repanda, and chlorpyriphos to 

M. discolor (Patnaik, 1983). Rabbi et. al. (1993) from Bangladesh observed that cypermethrin, alpha 

cypermethrin, diazinon, malathion, fenitrothion and phosphamidon caused low mortalities of the coccinellid 

predator, M. discolor among 28 insecticide formulations tested under field conditions. The predatory 

carabid beetle, Ophionea indica, which is predatory on BPH, was numerically affected by need-based 

application of carbofuran or schedule based application of carbofuran and monocrotophos (Ullah and 

Jahan 2004). 

EFFECT OF INSECTICIDES ON NATURAL ENEMIES OF LEAF FOLDER 

Methamidophos was recommended against leaf folder in China. However, the proper timing of the insecticide 

is very essential. Zhuge (1982) suggested that peak of the 3 rd instar of C. medinalis was the most 

opportune time for maximum effectiveness against the unparasitized larvae and minimum mortality of 

parasitized larvae. However, Zhu et al., (2000) observed that the rate of parasitism by Trichogramma 

spp. was significantly affected in plots treated with methamidophos. 

64 

Coccinellid Adult Coccinellid Grub

Tetrastichus sp. 

Trichogramma japonicum 


Effect of insecticides on egg parasitoides of stem borers 

Among various parasitoids, which have been recorded on eggs of 

various stem borers in rice ecosystem, Trichogramma japonicum, 

Trichogramma chilonis, Telenomus dignoides and Tetrastichus 

schoenobi are the most important ones. Hence, an attempt has been 

made to present the information available on the toxicity of various 

insecticides on these parasitoids separately. 

A long-term data of 10 years were utilized for evolving the effect of 

chlordimeform, an insecticide routinely used in China for suppressing 

the populations of YSB, on the egg parasite T. japonicum (Hong 

1990). The results showed that spraying of the insecticide was more 

harmful to the parasite than drenching or soil application. The 

hatching of the parasite was more adversely affected if spraying 

was done 2 days earlier to hatching of host eggs. Ye (1988) from 

Nanchang, Jiangxi China observed that of the 8 pesticides commonly Trichogramma sp. 

used against YSB, azinphos-methyl, and tetrachlorvinphos caused 

lower mortality of the egg parasitoid while piperiphos caused the greatest mortality. Other insecticides 

which exhibited moderate adverse effect on T. japonicum were chlormephos-ethyl, primiphos-ethyl, 

methamidophos. In general in areas where large quantities of pesticides were used, the egg parasitism 

was 1-5 % compared to 24% in areas of lower pesticide usage. Adults of the parasitoid were more 

susceptible than the larvae or pupae of the parasitoid. 

A detailed laboratory study in DRR (India) based on rate of parasitisation, and emergence of adults of 

the parasite revealed that chlorpyriphos and quinalphos at recommended concentration (0.05%) adversely 

affected parasitization. (Jhansi lakshmi et al., 1997b). However, comparatively less adverse effect was 

observed with regard to neem formulations. A field cum laboratory study by Samanta et. al. (2005) to 

evaluate the persistence of synthetic pyrethroid insecticides against YSB egg parasitoids, T. japonicum 

and T. chilonis revealed that fluvalinate recorded higher persistency against T. japonicum compared to T. 

chilonis, while, reverse trend was observed in case of deltamethrin. Among the others, lindane showed 

highest persistency while monocrotophos and quinalphos exhibited moderate persistence. 

Telenomus dignoides 

Continuous efforts by the scientists of Punjab Agricultural University, Ludhiana, India to evaluate the 

adverse effects of insecticides on T. dignoides, revealed that in general, granular formulations of phorate, 

carbofuran, quinalphos and cartap (35-40% parasitism) were less toxic than the spray formulations of 

chlorpyriphos, monocrotophos and quinalphos and acephate (5-25%) (Singh et al., 1994; Singh and 

Sharma 1998). In detailed further investigations, Singh et. al. (2003) observed that granules of cartap 

65


Table 11 : Relative safety of selected insecticides to predators of plant- and leafhoppers 

Thiomethoxam (Actara 25WG) 50 2800a 2800a 1573b 1817b 700a 

Thiomethoxam (Actara 25WG) 25 2688ab 2576ab 1253c 1722bc 700a 

Thiomethoxam (‘Actara 25WG) 12 2338b 2366b 1072c 1479c 665a 

Imidacloprid (Confidor 200SL) 50 2800a 2450ab 1458b 1624bc 691a 

Fipronil (Regent 5SC) 100 2688ab 2716ab 2058a 2478a 126c 

Figures in a column followed by same letter are not significantly different at 0. 05 by DMRT 

66 

Telenomus sp. 

Insecticide Conc 

hydrochloride at 0.5 and 1.0 kg a.i./ha was selective and 

safer to T.dignoides apart from other granular insecticides 

like carbofuran, phorate and monocrotophos and 

chlorpyriphos sprays. Cartap granules recorded a mean 

parasitism of 62 -82% compared to 40-59% in carbofuran, 

33-54% in phorate and 86.55% in untreated control. 

DEVELOPMENT OF INSECTICIDE RESISTANT STRAINS OF T. japonicum 

It is generally suggested that by using insecticide resistant strains of the parasitoids, it is possible to 

suppress insect populations of pests, by integrating insecticide application with inundative release of 

effective egg parasitoids. In detailed investigations in China by Xu et. al. (1986), the parasites were 

selected in all stages with 9-14 treatments of parathion-methyl, methamidophos, phosphamidon, MIPC, 

fenvalerate, and deltamethrin over 16-44 generations. Towards the end of the experiment, the LC 50 of 

eggs of resistant strain had increased 6.4 times to fenvalerate, 4.03 times to deltamethrin, 1.62 times to 

methamidophos and 0.82 times to phsphamidon in comparison to the concentrations of insecticides 

generally used in rice ecosystem. This offers clues that this approach is not a practical proposition for 

management of YSB. 

C. lividipennis T. parviceps M.atrolineata 

Nymphs Adults Nymphs Adults Adults 

24h 24h 24h 24h 24h 

(Jhansi lakshmi et. al. 2001a&b)


INSECTICIDE RESISTANCE IN RICE PESTS 

“Insecticide resistance” has been defined as the ability of a strain or a population of a pest species to 

survive and multiply at a dose of an insecticide, which is lethal to majority of the individuals of a normal 

population of that pest species´ It is a phenomenon that results due to varied biochemical mechanisms in 

the resistant population although the behavioral mechanisms like avoiding the insecticide treated surface 

by the pest cannot be ruled out. The biological mechanisms might be 

1) Reduced penetration of insecticide through integument or body wall of the insect species. 

2) Reduced transportation of the insecticide through the body cavity rendering lesser quantity of the 

insecticide reaching the target of action. 

3) Enhanced metabolism of the insecticide in the insect body due to higher titers of the enzymes like 

carboxyl esterases, phosphatases, multi-function oxidases, glutathione s-alkyl transferases which are 

general enzymes handling a variety of insecticide substrates. The enzymes may be more specific ones 

like DDT-dehydrochlorinase. 

4) Another biochemical lesion often associated with insecticide resistance in insect pests is reduced 

sensitivity of target of action. In case of organophosphates and carbamates it could be less sensitive 

acetyl cholinesterase or in case of nicotinoids and neiris-toxins it could be reduced binding of these 

insecticides with nicotinic acetylcholine receptors. In case of organochlorine insecticides like endosulfan, 

DDT or HCH it could be change in nerve membranes of insects leading to lesser binding of these insecticides 

to specific sites. In case of synthetic pyrethroids the lesser binding with target sites in nerve membranes 

may lead to lower knockdown resistance (kdr). 

5) The selection pressure on insect pest species which depends again on insecticide dosage, method and 

frequency of application and the mobility of target insect pest, plays an important role in the development 

of insecticide resistance. In general, low selection pressure leads to slower resistance development. But, 

it is not always necessary that high selection pressure will lead to faster resistance development. Usually, 

it is optimum selection pressure that may lead to faster resistance development in target pest species 

against the particular insecticide or a group of insecticides. This again depends on frequency of gene 

alleles conferring resistance mechanism(s) present in a given population of the pest species in an area. 

6) Same mechanism of resistance may not always be responsible in all populations of pest species 

present in different areas even against the same insecticide. Therefore, it is very important to understand 

the basic mechanism(s) of resistance present in different species of insect pests to a particular insecticide 

or a group of insecticides. It is in this complex background of insecticide resistance, we have to view and 

understand the importance of collecting and arranging the information available on insecticide resistance 

to various insect pests of rice crop. 

Since the inception of synthetic pesticide use in agriculture after Second World War, organochlorines, 

organophosphates, carbamates have been very extensively used against many insect pest species in rice. 

Therefore, the insect pests might have developed some mechanisms like reduced penetration and enhanced 

67


metabolism and target insensitivity, which might be common with other insecticides. In such cases, the 

development of resistance in a target population to new insecticides could be faster. 

Cross resistance and multiple resistance 

At this juncture, it is very important to clarify the terms cross resistance and multiple resistance. If a 

population of an insect pest is exposed continuously to an insecticide, the population gets selected and 

becomes resistant to that particular insecticide. If that particular population or strain also exhibits resistance 

to an insecticide to which that particular population was never exposed, then the phenomenon is called 

“cross resistance”. For instance, if rice brown planthopper is continuously sprayed with an 

organophosphate, monocrotophos in a given area, the population is likely to become resistant to 

monocrotophos. If the mechanism of resistance in that brown planthopper population or strain happens 

to be insensitivity of the target of action i.e., acetyl cholinesterase enzyme in insect nervous system, then 

there will be resistance to other organophosphates like phosphamidon, triazophos, dicrotophos etc or 

even to carbamates like carbaryl and carbofuran. Then, it is said, that particular population of BPH has 

exhibited cross resistance to these organophosphates and carbamates. At the same time, the BPH 

population may not exhibit cross resistance to synthetic pyrethroids, neiristoxins and neonicotinoids with 

entirely different mode of action. 

Multiple resistance is a phenomenon that exists when a population of an insect pest is simultaneously 

exposed to two or more insecticides usually belonging to groups with different modes of action, then the 

population may develop resistance to all those insecticides to which the insect population was exposed. 

For instance, whitebacked planthopper, Sogatella furcifera is selected with carbaryl (a carbamate insecticide), 

whose target of action is acetylcholinesterase enzyme in insect nervous system and imidacloprid (a 

neonicotinoid insecticide) or cartap hydrochloride (a neiris toxin insecticide) which block the nicotinic 

acetyl choline receptors in insect nervous system, then that population of whitebacked planthopper may 

become resistant to both carbamates (may be even to organophosphates) and imidacloprid or cartap (or 

even to other insecticides with similar mode of action). This happens only, when the resistant population 

has acquired resistance through the target insensitivity as the major mechanism of resistance. Then it is 

said to have developed multiple resistance. 

Brown planthopper Nilaparvata lugens 

The detailed information on insecticide resistance in BPH is available elsewhere (Krishnaiah et al., 2006). 

Hence, only abridged information on this aspect is presented below. 

1. SURVEY OF INSECTICIDE RESISTANCE IN FIELD POPULATIONS 

Studies In China And Taiwan: 

Insecticide resistance in field collected BPH, to MIPC and MTMC was reported as early as 1978 by Lin and 

Sun. In further studies, Sun et al., (1984a) showed that populations of N. lugens collected on rice in 

68


Taiwan were found to possess a high level of resistance to malathion and various levels of resistance to 

isoprocarb and some other insecticides. Wang and Ku (1984) compared the toxicities of 14 insecticides 

in 1977-83 with those in 1976. In 1980, resistance to carbaryl increased 8.4 fold and that to carbofuran 

14.8 fold, resistance to malathion and monocrotophos reached a record high level. In 1981 and 1982, 

resistance to most carbamates and organophosphates decreased gradually, but in 1983 resistance to all 

14 insecticides was again high. In 1982, resistance to 4 insecticides varied from 2.4- to 15.5- fold in 6 

localities and in 1983 the variation was from 2.4 to 6.4 fold. Monthly changes in insecticide resistance in 

planthoppers collected in September-November 1983 varied significantly, suggesting that migration was 

one of the factors affecting resistance. 

Wang et al., (1988a) studied the local variations in resistance to the insecticides carbaryl, carbofuran, 

malathion and monocrotophos between 1982 and 1984 in the rice delphacid N. lugens, of Central Taiwan. 

The ratio of maximum to minimum LC50 varied from 2.4- to 15.5- fold for BPH collected during the 

autumn in 1982-84, but only 2.3 to 2.9 fold in surveys carried out during the spring crop of 1984. In 

further studies, Cheng and Wang (1993) monitored insecticide resistance of N. lugens in China in 1986- 

89, considering the local and annual variations. Wang et al., (1997) monitored the susceptibility of N. lugens 

to insecticides in the lower Yangtze valley from 1991-1995 and concluded that the resistance varied little 

though there was fluctuation in the LD S0 values. 

B) Studies in Japan: 

Nagata (1983) observed resistance in immigrants of brown planthopper possibly resulting from changes in 

the origin of the migrants. Knowledge of geographical variation in this species was important to determine 

the source of migration. Nagata (1984) further noted that among insect pests of rice in Japan N. lugens has 

been relatively slow in developing resistance to insecticides. Comparisons of various immigrant populations 

revealed differences in insecticide resistance among immigrants. 

Endo et al., (1988a) studied the susceptibility of N. lugens to various insecticides using population 

collected in Japan in 1980 and 1987. A comparison of the results obtained in these experiments with previous 

data collected in 1967 showed that the susceptibility of N. lugens to organophosphates in 1987 was 

greater than in 1980. 

Hirai (1993) studied recent trends of insecticide susceptibility in the BPH in Japan. The susceptibility to BPMC 

[fenobucarb] MTMC [metolcarb], MIPC [isoprocarb], carbaryl, carbofuran, diazinon, malathion and propaphos 

fluctuated greatly at levels which indicated some degree of resistance. Hirai (1994) reviewed current status 

of insecticide susceptibility to BPMC [fenobucarb], MTMC [metolcarb], carbaryl, carbofuran, diazinon, malathion 

and propaphos for immigrant N. lugens on rice in Nagasaki, Kyushu, Japan. The pest had developed 

resistance to carbamates and organophosphates in the second half of the 1970’s and had remained 

moderately resistant from the beginning of the 1980's to 1993. 

69


C) Studies in Philippines: 

A field strain of N. lugens at the 1RRI in the Philippines, exposed to carbofuran for several years had developed 

resistance to the compound. Both sexes were seven times as resistant to carbofuran as compared to a 

greenhouse strain not exposed to insecticides and 2-5 times as resistant as the greenhouse strain to 

other insecticides used to varying extents on the IRRI farm, including monocrotophos and isoprocarb 

[MIPC]. (Heinrichs and Tetangco, 1978). 

Mochida and Basilio (1983) found that insecticide induced mortality among populations of the BPH collected 

from IRRI farm in the Philippines is much lower than that among greenhouse populations. The development 

of resistance among the field populations has undoubtedly been favoured by the applications of a mixture of 

chlorpyriphos and BPMC since 1978 and of acephate since 1981. Fabellar and Mochida (1985) reported 

that field collected populations which had prior exposure to insecticides showed significant level of resistance to 

BPMC (Fenobucarb) but did not appear to have developed resistance to carbaryl, carbofuran or MTMC 

(metolcarb) as compared to greenhouse populations. 

II. MECHANISM OF RESISTANCE AND STRATEGIES FOR OVERCOMING RESISTANCE IN BPH 

Studies in China and Taiwan: 

Dai and Sun (1984) found that, Taiwanese field strains of BPH resistant to many organophosphates 

(OPs) and carbamate insecticides, developed much higher resistance to pyrethroids without an alphacyano 

group. High esterase activity associated with OPs and carbamate resistance in Nilaparvata lugens conferred 

a major part of the resistance to permethrin and other primary alcohol ester pyrethroids. In addition, the 

ester linkage of these pyrethroids without an alpha cyanogroup might be vulnerable to oxidative cleavage. 

Permethrin, phenothrin and fenpropathrin were synergized by piperonyl butoxide and TBPT in the 

resistant strains, while only phenothrin was synergized in the susceptible strain. Cypermethrin was 

synergized only to a very limited extent, thus suggesting limited metabolism in these strains. 

Wang et al., (1988b) showed that the frequency of individuals with high aliesterase [carboxyl esterase] 

activity increased gradually in each generation selected by carbofuran. In strains selected successively 

with carbaryl and malathion, carbofuran and malathion, carbaryl and monocrotophos and carbofuran 

and monocrotophos over 8 generations, the LC values were the same as that of the original susceptible 

50 

strain. The LC increased by 5 and 6.5 fold after selection-for 8 generations with methamidophos 

50 

and buprofezin, respectively on Hybrid Shanyou 63 (Liu-Xianjin et al., 1996). 

Sun and Chen (1993) reported more than 10 molecular forms of carboxyl esterases with a -naphthyl 

acetate as a substrate in the delphacid. It was proposed that gene encoding the enzymes was expressed 

to a greater extent in resistant than in susceptible planthoppers. The resistant strain had higher activity 

and quantity of carboxyl esterases (preferably of the El type of active form) than the susceptible insects. 

The carboxyl esterases of N. lugens being unable to hydrolyse parathion could bind strongly to the 

potent anti-choline esterases paraoxon and oxon of several organophosphate compounds (Chen and 

Sun. 1994). 

70

Studies in Japan: 


Endo et. al. (1988a) studied the development and mechanism of insecticide resistance in the N. 

lugens, which was collected, from the field in Japan and selected with malathion or MTMC (metolcarb). The 

susceptibility of malathion and metolcarb selected strain to malathion decreased to 1/39 and 1/25, 

respectively of the initial level after 45 selections, while that to metolcarb decreased to 1/2.5 and 1/ 

4.2. Several synergists were tested with these insecticides, and of these 2-phenyl-4 H-l, 3,2 - 

benzodioxaphosphorin 2-oxide and 2-phenoxy-4H-l,3,2benzo-dioxaphosphorin 2-oxide were most 

effective and inhibited the decomposition of malaoxon. Malathion resistance is caused by high degradative 

activity to malathion and malaoxon and metolcarb resistance by low sensitivity of acetyl cholinesterase. 

Aliesterase activity and insensitivity to AchE were related to resistance in BPH to OP and carbamate 

compounds, respectively (Hama and Hosoda, 1983). 

Studies in Korea: 

Kim and Hwang (1987) investigated biochemical differences between strains of N. lugens resistant 

to organophosphorus insecticides, susceptible to them or hybrids between resistant and susceptible 

strains in the laboratory. Esterase isoenzyme activity was much greater in the resistant than in the 

susceptible strain. Esterase activity in delphacids treated with diazinon, fenitrothion or BPMC 

[fenobucarb] was not decreased in the resistant strain or in the F1 hybrids but was markedly decreased 

in the susceptible strain, as compared with untreated delphacid. 

III Neonicotinoid resistance in N. lugens and cross-resistance patterns 

Liu et al., (2003) from Nanjing, China, collected the field population of BPH and selected for imidacloprid 

resistance in the laboratory. The resistance increased by 11.35 times in 25 generations in the field 

collected population and the resistance ratio reached 72.83 compared with a laboratory susceptible 

strain. The selected resistant strain showed cross resistance to all the acetylcholine receptor targeting 

insecticides like monosultap (1.44 fold), acetamiprid (1.61 fold) and imidacloprid homologues JS599 

(2.46 fold) and JS598 (3.17 fold). But there was no cross resistance to other groups of insecticides. They 

demonstrated that Triphenyl phosphate (TPP) and Diethyl maleate (DEM) had no synergism with 

imidacloprid. However, PBO displayed significant synergism in some different strains and the synergism 

increased with resistance (S strain 1.2 fold; field population 1.43 fold; R strain 2.93 fold). PBO synergism 

to cross resistant insecticides was also found in the resistant strain (monosultap 1.25 fold; acetamiprid 

1.39 fold; JS598 1.94 fold; JS599 2.02 fold). It was concluded that esterase and glutathione S-transferase 

play little role in imidacloprid detoxification. The increase of P450-monoxygenases detoxification is an 

important mechanism for imidacloprid resistance and target insensitivity may also exist in N. lugens. 

Krishnaiah et al., (2002) in their green house studies on resistance development to monocrotophos and 

a neem formulation (NG-4 with 300 ppm azadirachtin) in green house strain of BPH (N. lugens) exposed 

the insect to LD 50 - LD 80 levels of these materials for 26 generations. Mono strain of BPH developed cross 

71


resistance to NG-4; ethofenprox and imidacloprid but remained susceptible to BPMC and cartap, while 

NG-4 strains of BPH continued to be susceptible to monocrotophos, ethofenprox, BPMC, cartap and 

imidacloprid. 

Krishnaiah et al., (2006) exposed susceptible glasshouse populations and field populations of BPH from 

the endemic areas of East and West Godavari districts of Andhra Pradesh to neonicotinoids like imidacloprid, 

thiamethoxam and clothianidin and phenyl pyrazole compounds like fipronil and ethiprole. The LC (ppm) 50 

against greenhouse populations for imidacloprid, thiamethoxam and clothianidin were 0.411, 0.369 and 

1.175 respectively while the LC (ppm) values for East Godavari populations were 14.44, 3.979 and 

50 

5.814 respectively. This showed the resistance ratios of 35.13; 10.78; 4.948 for imidacloprid, thiamethoxam 

and clothianidin in East Godavari populations. The LC (ppm) values for glasshouse populations against 

50 

fipronil and ethiprole were 0.383 and 0.569 ppm respectively while for East Godavari populations the 

corresponding values were 0.351 and 0.353 ppm respectively. The resistance ratios for fipronil and 

ethiprole in East Godavari populations were 0.916 and 0.623 respectively. These results reveal that East 

Godavari populations of BPH exhibited considerable resistance against all the three neonicotinoid 

insecticides at the same time there was no cross resistance to the phenyl pyrazole compounds (fipronil 

and ethiprole) in these East Godavari populations (Table 12 ). 

Biological Fitness of Imidacloprid Resistant Strain of BPH 

Liu et al., (2003a) studied the effect of imidacloprid resistance on the fitness of BPH in terms of 

developmental and reproductive characteristics by constructing and comparing the life tables of the two 

resistant strains (R 1 , R 2 ) with those of the susceptible strain. The results showed that both R1 and R 2 

strains had developmental disadvantages, including a lower larval survival rate from neonate to 2 nd 

instar, a lower adult emergence rate and shorter female life span. The reproductive disadvantages included 

72 

Table 12 : LC 50 (ppm) values for insecticides against East Godavari and greenhouse 

populations of BPH 

Insecticide Group 

East Godavari 

population 

LC50 (ppm) 

Greenhouse 

population 

Resistance 

ratio 

Imidacloprid NN 14.44 0.411 35.13 

Thiamethoxam NN 3.979 0.369 10.78 

Clothianididn NN 5.814 1.175 4.948 

Fipronil PP 0.351 0.383 0.916 

Ethiprole PP 0.353 0.569 0.623 

NN: neonicotinoid PP: phenyl pyrazole 

(Krishnaiah et. al. 2006)


lower copulation rate, fecundity and hatchability. In addition, the R 2 strain had prolonged egg duration 

and a lower larval survival rate from the 3 rd to 5 th instar. The fastigium of R 2 was lower than that of S and 

F 2. The fitness of the two resistant strains was determined by comparing the population number tendency 

index (I) with the susceptible strain as standard. The relative fitness value for R 1 strain was calculated to 

be 0.609 and the R 2 strain was only 0.245. 

White backed planthopper, Sogatella furcifera 

The reports of insecticide resistance in WBPH are mainly from Japan and China. Hosoda (1989) compared 

the topical LD 50s of 7 field collected strains from different parts in Japan with the reference strain in the 

laboratory by topical application and observed 9 to 37 fold resistance to OPs like fenitrothion, malathion, 

fenthion, and phorate and relatively low level of resistance (2 to 3 fold) to carbamates like carbaryl and 

BPMC. Few years later, Hirai (1994) reported widespread and high level of resistance in WBPH to 

malathion but relatively low resistance to other OPs as well as carbamates. 

In studies in China, Yao et al., (2000) evaluated four populations from different provinces in China to three 

insecticides viz. malathion, methamidophos, and isoprocarb and the activity of 4 enzymes (esterases, 

carboxyl esterase, glutathione S-transferase, and acetyl cholinesterase) related to insecticide resistance 

were determined. They observed 16 to 137 times resistance to malathion and 10 to16 times resistance 

to isoprocarb compared to 1969 levels. Liu et al., (2001) evaluated six methods of selection for resistance 

in WBPH viz., topical treatment using hand microapplicator, topical application using capillary tube, spraying 

on rice seedlings, spraying on planthoppers, spraying on rice and planthoppers, soaking rice stems and 

concluded that spraying on rice and planthoppers was the best and most efficient method. 

(ii) Neonicotinoid resistance in WBPH 

Xaofei Ping et al., (2001) determined the insecticide susceptibility of WBPH collected from China and 

Japan in 1997 by topical application. The insecticide susceptibility of WBPH was not much different 

among the populations from Nagasaki (South West Japan), Hangzhou (Zhejiang, China) and Jinghong 

(Yunnan, China). The LD 50 s for WBPH were 0.047 – 0.062 mg/g for nitenpyram, 0.067 – 0.18mg/g for 

imidacloprid, 0.72 – 1.5 mg/g for silafluofen and 0.89 – 1.6 mg/g for ethofenprox, in contrast to 96 – 

130 mg/g for malathion and 100 mg/g for fenithrothion. Thus, the LD 50 s of chloronicotinyl and pyrethroids 

were much smaller than those of the organophosphates and organochlorines. The LD 50 of monocrotophos 

was 1/17 – 1/3 as large as that of the other organophosphates. The LD 50 s of isoprocarb and propoxur 

for WBPH populations collected in 1997 were 5 times as large as in 1989. Nagata et. al. (2002) from 

Ibaraki University, Ibaraki Japan simultaneously monitored the insecticide susceptibility of the long range 

migrating rice planthoppers like WBPH in Japan, China (3 locations) and Malaysia by standardized topical 

application method on 10 insecticides in 2000. The LD 50 of Japanese WBPH during 2000 coincided with 

those for the two Chinese populations, but one of the Chinese populations gave remarkably larger LD 50 for 

imidacloprid. The Malaysian population of WBPH gave LD 50 almost equal to those of the Japanese WBPH 

during 2000. 

73


Small brown planthopper Laodelphax striatellus 

Small brown planthopper is one of the most important pests infesting rice in Japan and transmitting stripe 

virus. Nagata and Ohiro (1986) observed 89 to 272 fold resistance to malathion, and 20 to 70 fold 

resistance to fenitrothion, diazinon, MTMC, carbaryl and MIPC. In five populations collected from different 

regions of Japan. Kassai and Ozaki (1984) made an attempt to observe the changes in level of resistance 

to different groups of insecticides when a SBPH population with 370 fold resistance was selected with the 

synthetic pyrethroid, fenvalerate. The restance to malathion decreased markedly, during the first 5-6 

generations and to one quarter of the original level by 19 th generation. During this period, the level of 

resistance to fenvalerate has increased 5 fold. Thus this shows the possibility of shifting to other groups 

of insecticides as a strategy to contain the increase in the level of resistance to originally used insecticides. 

Neonicotinoid Resistance in SBPH 

The smaller brown planthopper, Laodelphax striatellus Fallen (Homoptera: Delphacidae) is one of the 

most important insect pests infesting rice plants in Japan and transmitting the stripe virus. However, 

fortunately this hopper pest was not reported from any part of Indian subcontinent including Bangladesh 

and Pakistan except a stray observation at Punjab Agricultural University, Ludhiana during 1980. Since 

this pest also belongs to the same Delphacidae family to which BPH and WBPH belong, the information on 

the development of neonicotinoid resistance in SBPH and the possible mechanisms can give us insights in 

tackling neonicotinoid resistance in BPH and WBPH in India. 

Endo et al., (2002) from Ibaraki, Japan examined the insecticide susceptibility of L. striatellus collected 

from East Asia in 1992 – 1994 by topical application method. The LD values of organophosphorus 

50 

insecticides for the Northern Vietnam populations (HAI, HAN, VIN) and the JIN population (Yunan province, 

China) were lower than those of the FU (Zhejiang Province, China) IB (Central Japan) and KU (South 

western Japan) populations. The LD values of organophosphorus and carbamate insecticides for the 

50 

northern Vietnam populations were almost the same as that for Fukuoka (Western Japan) population 

examined in 1967. The LD values of organophosphorus insecticides did not differ among the FU (Zhejiang 

50 

Province, China), IB (Central Japan) and KU (South Western Japan) populations. The LD values of 

50 

carbamates for the KU population were the largest and those for northern Vietnam populations were the 

smallest. The carbamate susceptibility of acetylcholinesterase in the KU population was lower than that in 

the HAI population. Therefore, it was concluded that the insensitivity of acetylcholinesterase for carbamate 

was one of the carbamate resistant factors in the KU population. LD values of ethofenprox, fenvalerate 

50 

and imidacloprid showed no differences among all the populations tested. This showed that there was no 

cross resistance to ether derivatives (ethofenprox), synthetic pyrethroids (fenvalerate) and neonicotinoids 

(imidacloprid) in these carbamate resistant KU population of L. striatellus. 

Green leaf hopper Nephotettix cincticeps 

This insect pest, which is very important in Japan, has long been managed with organophosphate and 

carbamate insecticides till 1970s. Hama and Iwata (1971) reported that insensitivity of cholinesterase 

74


enzyme, the target of these insecticides was observed to be the major cause of resistance. Hama and his 

group continued their studies on this aspect. Faster degradation of propoxur, a carbamate insecticide in 

resistant strain was found to be the cause of resistance. (Hama et al., 1979; Hama, 1980; Hama et al., 

1980). In case of organophosphate resistance, particularly with regard to diazinon and fenitrothion, 

degradation of either the parent compounds or their oxons was observed to be the major cause of 

resistance and consequently use of synergists like IBP, piperonyl butoxide and sesamex enhanced the 

toxicity of these molecules in resistant strains. However, the enhancement was more pronounced in case 

of IBP than other synergists. 

Later studies by Motoyama et al., (1984) revealed that, in case of OP resistant strains also, degradation 

by carboxyesterases was the major factor for resistance to malathion but these carboxyesterases could 

also play a role as binding proteins for maloxon, the oxygen analog of malathion, thus reducing the 

amount of the toxicant available to the site of action, the cholinesterase enzyme in nervous system. When 

attempts were made to suppress the development of resistance to OP and carbamate resistance in GLH, 

N. cincticeps, it was observed that a remarkable synergism was shown by mixtures of fenvalerate and 

malathion (1:1) and fenvalerate and diazinon (1:1) against OP and carbamate resistant strains. Other 

synthetic pyrethroids like fenpropathrin and permethrin could also act as synergists in combination with 

OP and carbamates resistant insects (Yamamoto et al., 1993). 

Green leafhopper, Nephotettix virescens 

In case of another species of GLH, which is more important in India and Philippines, there are rare 

instances of resistance development to insecticides. Fabellar et. al. (1981) observed 1.32 to 2.02 fold 

resistance to acephate, parathion methyl and monocrotophos in populations collected from different 

regions in Philippines. Fabellar and Mochida (1985) observed that the resistance level ranging from 1.47 

to 3.22 to BPMC, carbaryl, carbofuran, diazinon and monocrotophos in similar populations. Thus, the 

insecticide resistance problem is not acute in N. virescens in Philippines. 

Leaf folder, Cnaphalocrocis medinalis 

If one observes the information on insecticide resistance in case of leaf folder, there are no systematic 

studies in any country probably because insecticide resistance is not a serious problem in leaf folder. The 

first report was by Endo et al., (1987) from Japan. They monitored the level of insecticide resistance by 

leafdip method for chlorpyriphos-methyl, dimethylvinphos, diazinon, acephate, monocrotophos and cartap. 

Moderate resistance (RR of 9.4) was observed in case of diazinon, but it was negligible for other insecticides 

(RR of 1.2 to 2.7). In another report from China, Xiang et al., (1994) observed low level of resistance (RR 

of 4.06) in Guangdong province to cartap and acephate. From India, the only report available is by 

Anandan and Regupathy (2002) where 4 th instar larvae were topically applied with monocrotophos, 

quinalphos, chlorpyriphos, and phosphamidon and noticed gradual increase in insecticide susceptibility 

with successive generations when field collected population was reared under glass house conditions. 

However, the level of resistance was negligible (0 to 22.4%) for different insecticides. 

75


Thus, the overall situation reveals the insecticide resistance is not a serious problem in rice leaf folder any 

where in the world. 

Yellow stem borer, Scirpophaga incertulas: 

There are two recent reports on assessment of insecticide resistance in YSB from China. Han et al., 

(1988) observed 2.5 to 3.6 times resistance to methamidophos and methyl parathion in shanghai 

populations compared to Jianxi populations by topical application on 3rd instar larvae. Shen et al., (1999) 

collected the egg masses of the pest from different locations and inoculated 3rd instar larva on 50 day old 

insecticide sprayed rice plants. The LC 50 values for methamidophos varied from 1.62 to 13.17 while it 

was negligible for other insecticides. The above information clearly shows that insecticide resistance is 

not a serious problem in the management of YSB. But this should be viewed with caution due to the 

following reasons. 

1. There are no artificial rearing methods for yellow stem borer and rearing on natural host (rice) is very 

tedious and time consuming. 

2. The survival of insecticide treated larvae after inoculation in rice plants is very low. Hence, the 

assessment on real toxicity levels of insecticides under laboratory conditions is very difficult. 

3. Assessment of level of insecticide resistance under field conditions is not accurate or also not easily 

possible. 

Hence, there appears to be no serious attempts on the part of rice entomologists to assess the level of 

insecticide resistance in YSB. 

Striped stem borer, Chilo suppressalis: 

Unlike in YSB, there is ample information available on insecticide resistance in case of SSB. The resistance 

is wide spread and the efforts put in also appears to be relatively very high owing o the ease with which 

this insect can be reared, handled and assessed for toxicity of insecticides. Konno et al., (1986) collected 

an organophosphate insecticide resistant strain of SSB from Japan and studied 61 organophosphates 

with varying structural groups. There was no resistance to OPs with ester bond having aliphatic enol or 

thioalcohol such as malathion, phenthoate, azinphos-methyl and monocrotophos in contrast to high level 

of resistance to those with aryl ester bond or heterocyclic esters. Konno and Kajihara (1985) observed 

a high degree of synergism between, fenitrothion and a carbamate pirimicarb (an aphicide). The team 

under the leadership of Konno continued investigations on OP resistance with special reference to 

fenitrothion. The penetration rates of fenitrothion in susceptible and resistant strains were similar but the 

detoxification of the toxic metabolite of fenitrothion viz. fenoxon in resistant strain appeared to be the 

major resistant mechanism to fenitrothion in resistant strains (Konno and Shishido, 1987 and 1991). 

Later studies showed that sequestering activity of carboxyl esterase enzyme for fenitroxon in fenitrothion 

resistant strain was highly correlated with resistance (Konno, 1996). 

However, simultaneous studies in China by Han et al., (1995) showed that resistance to fenitrothion was 

76


due to high activity of carboxyl esterases, mixed function oxidases, enhanced O-demethylation by MFO 

and insensitivity of acetyl cholinesterase the target enzyme of the compound. The later studies by Chinese 

group revealed that the populations of C. supressalis collected from different regions in china exhibited 

varying levels of resistance to different compounds. The populations from Zhejiang were moderately 

resistant to triazophos and the population from Hunan exhibited very low level of resistance to triazophos 

(Cao et al., 2001). Later, triazophos resistance became wide spread. A field collected population of C. 

supressalis with a resistance level of 203 increased resistance level to 787 fold after continuous selection 

with triazophos in the laboratory for eight generations. However, there was no cross resistance either to 

isocarbophos or methamydophos. The resistant strain had higher activity of esterase and microsomal 

o-demethylase than susceptible strain (Qu et al., 2003) . 

STRATEGIES TO OVERCOME INSECTICIDE RESISTANCE: 

The following are the basic strategies to retard the development of insecticide resistance in an insect 

pest. 

l Alternate application of effective insecticides belonging to different groups and different modes of 

action. 

l Adoption of other methods of pest management like cultural, biological and varietal means and utilizing 

insecticides to the minimum. 

l Use of suitable synergists along with effective insecticides to block the metabolic degradation of 

insecticides in insect system. 

l Continuation of insecticide evaluation programmes as a part of co-ordinated entomology agenda to 

identify new insecticides with different modes of action. This will help a great deal in overcoming the 

problem of insecticide resistance in rice pests in particular and all crop pests in general. 

CONCLUSIONS AND FUTURE THRUST 

l Among the insect pests of rice, detailed field surveys and studies on mechanism of insecticide resistance 

are available in case of BPH, N. lugens from japan and China. In India the information available on 

insecticide resistance in BPH is very limited. In view of wide spread occurrence of this pest in India, 

there is a need to identify the monitoring of insecticide resistance in BPH in different agro-ecological 

zones of rice by creating a permanent funding mechanism at least in National Centers of Rice Research 

like DRR and CRRI along with a few State Agricultural Universities (SAUs) where BPH is a major 

problem. 

l Yellow stem borer S. incertulas is still the most important insect pest of rice. In the absence of any 

dependable sources of host plant resistance to this pest, insecticides are widely used as the major 

means of checking YSB infestation. For instance, in states like Punjab as many as 5 sprays of 

77


recommended insecticides like cartap, monocrotophos, chlorpyriphos etc. are applied during a crop 

season. Under these circumstances, there must be slow development of insecticide resistance in this 

species. There is no baseline data of insecticides effectiveness against yellow stem borer to judge the 

level of insecticide resistance. Even the methodology for detection and quantification of resistance 

level to most commonly used insecticides is lacking. Therefore, this should also form a part of research 

agenda of insecticide resistance monitoring team of scientists. 

l Leaf folder, C. medinalis is another important insect pest from insecticide resistance point of view. 

This is becoming serious in traditional areas and also spreading to new areas. Here also insecticides 

are the major means of managing the pest. Further very effective insecticides like cartap, 

monocrotophos are being widely used. Hence the chances of leaf folder becoming resistant to these 

insecticides are high. Therefore, leaf folder should also be monitored for insecticide resistance 

development after evolving suitable methodology for detection and determination of base line data. 

This can be easily done in institutes where glasshouse facilities are available. 

l Basic studies on one or more of these pests regarding the fastness of resistance development, 

mechanism of resistance and strategies for management of insecticide resistance have to be conducted, 

when there is evidence of resistance development. 

l In view of high degree of effectiveness of neonicotinoids and lower cost involved per unit area, these 

insecticides are likely to be overused and abused by rice farmers in BPH endemic areas. This will 

further hasten the process of resistance development. 

l The information available on the practical methods for detecting and monitoring neonicotinoid resistance 

in rice planthoppers is inadequate and a lot of research efforts need to go into this aspect. 

l The biochemical mechanisms involved and cross-resistance patterns are very poorly understood and 

hence emphasis should also be laid on this aspect of neonicotinoid resistance. 

l The meager evidence indicates mainly the role of m.f.o. in degrading neonicotinoids in resistant 

strains of planthoppers. As m.f.o. are general degrading enzymes for all xenobiotics, it is likely that 

there will be cross resistance to other groups of insecticides in neonicotinoid resistant populations of 

planthoppers. Hence, this aspect also needs emphasis as a future thrust area of research. 

78


INSECTICIDE INDUCED INSECT RESURGENCE 

‘Pest resurgence’ or ‘flareback’ of the target and non-target organisms in a crop ecosystem is one of the 

harmful effects of insecticide use along with others like, environmental pollution, destruction of natural 

enemies, and harmful effects on domestic and wild life, harmful residues on food and fodder, 

biomagnification in terrestrial and aquatic ecosystems etc (Krishnaiah and Kalode, 1985). 

‘Resurgence’, in general, means a statistically significant increase in population of or damage by the 

target pests following pesticide application (Heinrichs et al., 1982 a and b). This appears to be the 

resultant effect of multiplicity of factors. 

Factors for resurgence: 

l Application of insecticides in an agro-ecosystem, where the target pest is killed to some extent reduces 

competition among survivors leading to increased multiplication. 

l Direct physiological stimulation of growth and reproduction of target pest may also occur (Hart and 

Ingle, 1971) 

l The effect on the target organism may be indirectly through the alteration in nutritional quality of the 

host plant. This may lead to favourable biological effects on target pests such as 

v shortening of the developmental period, 

v formation of vigorous and able bodied insects, which in turn survive better even in the 

adverse environment, and 

v increased rate of reproduction leading to better survival potential (Heinrichs and 

Mochida, 1983). 

l Destruction of natural enemies such as parasites and predators has been reported to be the major 

cause for insecticide induced resurgence of some, insect pests (Krishnaiah and Kalode, 1987). 

l Removal of alternate hosts of parasites, which act as reserves of food during the off season may 

occasionally lead to resurgence of target pests (lyatomi, 1951). 

l Agronomic practices such as excessive use of nitrogenous fertilizers and high plant density, which are 

generally favourable to pests, and use of susceptible varieties or hybrids may also result in resurgence 

of insect pests. 

l Favourable climatic conditions such as optimum temperature and humidity also aggravate the problem. 

In rice, insecticide-induced resurgence has been reported in case of the following: 

a) Brown planthopper (BPH) Nilaparvata lugens (Stal.), 

b) White backed planthopper (WBPH), Sogatella furcifera (Horvath), 

c) Leaf folder (LF), Cnaphalocrocis medinalis Guenee, 

79


d) Green leafhopper (GLH), Nephotettix cincticeps Jhler, 

e) Small brown planthopper (SBP), Laodelphax striatellus Fallon, 

f) Blue leafhopper (BLH), Zygina maculifrons Matsch, 

g) Striped stem borer (SSB), Chilo suppressalis Walker. 

However, most of the information on insecticide induced resurgence has been generated in case of 

BPH, WBPH and leaf folder. 

History of Insecticide Induced Resurgence in Rice 

The first instance of increased BPH population in tropics due to insecticide application was reported 

in 1968 in the experimental fields of International Rice Research Institute, Philippines, where the plots 

treated with gamma-HCH at the rate of 2.0 kg a.i./ha recorded approximately three times higher population of 

BPH than the untreated control (IRRI, 1969). Testing of synthetic pyrethroid, NRDC 161 (deltamethrin) in 

1976 resulted in dramatic increase in the population of BPH, showing a resurgence ratio of 56:1 with 

100 percent hopper burn (IRRI, 1977). Later on an increasing number of reports on the resurgence of 

BPH have been published from many tropical rice growing countries. BPH resurgence has been reported 

from Bangladesh (Alam and Karim, 1977), India (Varadarajan et al., 1977; AICRIP, 1978), Indonesia 

(Oka, 1978; Soekarna, 1979) and Solomon islands (Stapley, 1976). 

Causes of BPH Resurgence 

Insecticides causing resurgence have been identified and these include organophosphates, carbamates 

and synthetic pyrethroids. Several laboratory and field studies have indicated that reproductive stimulation 

in females receiving sub-lethal doses of insecticides and selective removal of natural enemies are major 

factors causing BPH resurgence. Degree of resurgence is affected by insecticide management practices 

such as rate, number, method, and time of application and by the level of varietal resistance to insects. 

Enhancement of Reproductive Rate under Laboratory conditions 

Direct effect of insecticides on reproductive rate of BPH has been measured by topically treating fifthinstar 

nymphs with doses of LD 5 to LD 50 of deltamethrin, methyl parathion and perthane. Highest 

reproductive stimulation occurred at the LD 25 dosage for methyl parathion and LD 50 for deltamethrin 

(Chelliah et al., 1980). Perthane did not cause reproductive stimulation at any of the dosages tested. 

However, the reasons for such reproductive stimulation could not be elucidated. Increase in reproductive 

rate can occur through changes in host plant for better nutritive quality. When plants were sprayed with 

deltamethrin, diazinon, methylparathion and perthane at 10 day interval, followed by confinement of BPH 

adults after the toxic effect was lost, there was a significant increase in the reproductive rate of the 

hoppers confined on plants treated with methylparathion, deltamethrin, and diazinon (Chelliah and Heinrichs, 

1980). However, hoppers on perthane treated plants had significantly fewer nymphs than on the untreated 

control. 

80

Resurgence of BPH under Field conditions 


The amount of toxicant that comes in contact with N. lugens and its predators is influenced by several 

factors. The density of the crop canopy increases with age of the crop, limiting the spray material reaching 

the base of the plant, where BPH feeds. Rainfall, which washes the insecticide from the plant, and degree 

of resistance to insecticides are additional factors influencing BPH resurgence under field conditions 

(Heinrichs et al., 1982b). The situation is further complicated because the insecticide application rates, 

application methods, time of application and degree of varietal resistance could also influence the level 

of BPH resurgence (Heinrichs and Mochida, 1983). 

Effect of Rates of Insecticide Application on BPH and its Predators 

When foliar sprays of methyl parathion, deltamethrin, diazinon and carbosulfan (FMC 35001) were applied 

at different dosages, higher concentrations of carbosulfan in general led to greater populations of BPH 

(Heinrichs et al., 1982 b). Among the three predators of BPH (spiders, Microvelia atrolineata Bergoth 

and Cyrtorhinus lividipennis Reuter), deltamethrin was the most toxic to spiders even at low rates; 

deltamethrin and carbosulfan were toxic to M. atrolineata, while diazinon was less toxic to both spiders 

and M. atrolineata. High rates of all the insecticides resulted in lowest populations of C. lividipennis 

(Heinrichs and Mochida, 1983). Krishnaiah and Kalode (1987) observed that insecticides such as 

monocrotophos, phosalone and phosphamidon at recommended concentrations (0.05%) checked BPH 

build-up while monocrotophos and phosphamidon at suboptimal concentrations (0.02%) resulted in 

resurgence. Among the other insecticides deltamethrin at recommended concentration (0.01% and 

0.005%) recorded highest BPH population whereas methylparathion and fenvalerate exhibited a tendency 

towards BPH resurgence. Deltamethrin also showed high degree of adverse affect on natural enemies 

such as mirid bug, C. lividipennis and spiders. Since, resurgence is a dose dependant phenomenon, 

emphasis should be placed on the application of correct dosage of effective and recommended insecticides 

in addition to selecting the right insecticide (Krishnaiah and Kalode, 1987). 

Number, time and Method of insecticide Application and Pest Resurgence 

In the tropics, the most popular method of insecticide application is by foliar spraying. According to 

Heinrichs et al., (1982a} application of insecticides through foliar spraying induces high degree of BPH 

resurgence when compared to application as root zone placement, and as broadcasting. Under field 

conditions, dust formulations control BPH, but foliar spraying with insecticides results in resurgence 

(Raman, 1981). Application of granular gamma HCH, diazinon, Sevidol (Chelliah and Heinrichs, 1979), 

mephospholan, and quinalphos (Varadarajan et al., 1977) was observed to cause BPH resurgence. 

Resurgence was also influenced by the time of application. Sprays of methyl parthion and deltamethrin 

applied at 50 and 65 days after transplanting induced resurgence, while earlier applications had little 

effect. Further, plots receiving only one application had low BPH population as compared to those 

sprayed 2, 3 or 4 times (Heinrichs and Mochida, 1983). 

81


Number of Sprays and Feeding 

The excretion of honeydew by BPH has been directly correlated to the rate of feeding (Sogawa and Pathak, 

1970). Chelliah and Heinrichs (1980} observed that spraying with deltamethrin, methyl parathion, and 

diazinon increased BPH feeding rate by 61, 43, and 33 percent, respectively compared to check. 

Raman and Uthamasamy (1983a) reported that the feeding rate is high in plants treated with deltamethrin, 

methylparathion, quinalphos, cypermethrin, fenthion, and permethrin. On the contrary, in fenvalerate, 

phosphamidon, BPMC, carbosulfan, and methamidophos treated plants, the feeding rate is lower than 

that of untreated check. 

Resurgence and Sex Ratio 

The sex ratio of adults resulting from nymphs reared on insecticide-treated plants was in favour of 

females compared to those on untreated control. The sex ratio of methyl-parathion and deltamethrin 

treated plants is 1.26 and 1.46 respectively, compared to 1.00 on untreated plants (Chelliah, 1979). 

Raman and Uthamasamy (1983a) observed that, of the eight insecticides evaluated for pest resurgence, 

the sex ratio was in favour of females in all, except in phosphamidon treated plants. 

Resurgence through Population Changes in Natural Enemies 

Reduction in the population of natural enemies following insecticide application has been suggested as 

an important factor for BPH resurgence (Kobayashi 1961; Miyashita 1963; Kiritani et al., 1971; Kiritani, 

1972; 1975; Raman and Uthamasamy, 1983b, Krishnaiah and Kalode, 1987). Dyck and Orlido (1977) 

reported that reduction in the population of mirid predator, C. lividipennis after regular spraying with 

methyl-parathion causes BPH resurgence. However, under field conditions, increase in populations 

of spiders, C. lividipennis and M. atrolineata was not proportionate to the reduction in BPH population 

(Reissig et al., 1982a). However, Chelliah (1979) and Heinrichs et al., (1982b) concluded that natural 

enemy destruction is a minor factor in BPH resurgence. Field studies conducted by Krishnaiah and 

Kalode (1993a) showed that the population of mirid bug (MB) C. lividipennis depended on the population 

of BPH. However, BPH/MB ratio was the highest in deltamethrin (1311) and the lowest in ethofenprox (an 

ether derivative) at 100 g a.i./ha (9.8), which did not cause resurgence. 

Resurgence through varietal Interaction and Plant Architecture 

When IR 29, IR 40, and IR 42 (respectively susceptible, moderately resistant, and resistant to BPH in the 

Philippines) were tested for their’ influence on deltamethrin induced BPH resurgence, the maximum 

population increases were 74 : 50, and 5 fold, respectively as compared to check. This demonstrated 

the value of host plant resistance in lowering the BPH resurgence (Reissig et al., 1982b). Chelliah (1979) 

reported that the reproductive rate and BPH feeding on the susceptible TN1 sprayed with deltamethrin 

and methyl-parathion were markedly greater than those feeding on unsprayed plants. However, in all the 

three resistant cultivars (IR 26, Mudgo, and ASD 7) tested, the insecticides did not cause resurgence of the 

pest. 

82


Effect of insecticides in influencing the plant growth is one of the factors for the resurgence of insects. 

Cheiliah and Heinrichs (1979) reported that carbosulfan, perthane, and methylparathion increased 

the number of tillers. Diazinon and perthane sprayed plants grow taller than the unsprayed plants. 

Raman and Uthamasamy (1983a) observed that foliar application of deltamethrin and methyl parathion 

resulted in increased numbers of tillers and leaves, and stimulated plant growth. Thus, the changes in 

plant architecture as a result of phytotonic effect of certain insecticides may attract more macropterous 

hoppers immigrating into the rice fields. Increased alighting followed by increased feeding, reproduction 

and longevity augment BPH resurgence. 

Hormonal Influence of Resurgence through Increased Reproduction 

According to Roan and Hopkins (1961), sub-lethal doses of toxicants might excite nerve activity and 

could bring about a favourable neurohormonal influence on insect reproduction. The liberation of massive 

amounts of hormone is a lethal step of insecticidal action. A sub-lethal amount of an insecticide can 

result in the production of a neurohormone, which in turn can stimulate the reproductive potential of an 

insect leading to insect resurgence. However, critical investigations are essential to determine the specific 

hormonal influence on the reproductive system of the insects. 

Resurgence of whitebacked planthopper, Sogatella furcifera (Horvath) 

Although, intensive field studies on synthetic pyrethroid induced resurgence of WBPH are lacking in 

literature, a number of observations have been made in recent years that the synthetic pyrethroids like 

deltamethrin (25 g a.i./ ha), lambda cyhalothrin (12.5g a.i./ha), betacyfluthrin (12.5 g a.i./ha), 

registered significantly higher populations of WBPH than untreated control (DRR, 1998 - 2002). The 

neonicotinoid insecticides like imidacloprid (25 g a.i./ha) and thiamethoxam (25 g a.i./ha) and insect 

growth regulator buprofezin (100-200g a.i./ha) could effectively check WBPH populations when used 

alone and also suppressed the resurgence causing property of synthetic pyrethroids, when used as 

combination formulations (one neonicotinoid + one synthetic pyrethroid) or as tank mixing of straight 

formulations (DRR, 1998-2002). A greenhouse study at IRRI on the influence of varietal resistance on 

resurgence causing property of deltamethrin revealed that the insecticide caused a significant increase 

in population growth of WBPH in highly resistant (IR 2035-117-3), resistant (ARC 10239) and susceptible 

(TN1) cuitivars and increase in nymphal survival and growth index on TN1 (Salim and Heinrichs, 1987). 

Resurgence in Rice Leaf folder Cnaphalocrocis medinalis Guenee 

Chelliah and Heinrichs (1984) reported that resurgence of leaf folder could be noticed after the application 

of phorate 10G coupled with adoption of close plant spacing and application of high dose of nitrogen 

fertilizer. This might be due to promotion of plant growth leading to heavy leaf folder infestation. Insecticide 

induced leaf folder infestation has also been reported by Subramanian et al., (1985). Seedling root dip in 

chlorpyriphos (0.02%) for 12 h, followed by broadcasting of carbofuran 3G (1.0 kg a.i./ha) at 20, 40, 

and 60 DAT (days after transplanting) showed high levels of leaf folder infestation at 75 DAT compared 

83


with the untreated plots. At Pondicherry, broadcast application of phorate 10G @ 1.0 kg a.i./ha at 20 and 

40 DAT resulted in build up of leaf folder, recording 990 damaged leaves/20 hills as compared to 164 

damaged leaves/20 hills in untreated control (DRR, 1994). However, broadcasting of carbofuran 3G @ 

0.75 kg a.i./ha at 20 and 40 DAT did not cause resurgence of leaf folder (43.3 damaged leaves/ 20 

hills). Against leaf folder, broadcast application of cartap granules @ 1.0 kg a.i./ha or spraying with 

cartap WP @ 300 g a.i. /ha could successfully check the build up of the pest when used at 60 DAT as a 

follow up treatment to phorate @ 1.0 kg a.i./ha applied at 20 and 40 DAT (DRR, 1994 and Krishnaiah et 

al., 1995). 

Of late, the spray of neonicotinoids like imidacloprid (20 g a.i./ha) registered significantly higher 

leaf folder damage (177 to 232 ADL /10 hills) than untreated control (28 to 56 ADL/10 hills) as observed 

at Jagtial during kharif 2001 (DRR, 2001). In the same experiment, the synthetic pyrethroid 

betacyfluthrin @ 12.5 g a.i./ha (10 to 22 ADL /10 hills) and the combination of betacyfluthrin + imidacloprid 

@ 15 + 15 g a.i./ha (18 to 39 ADL / 10 hills) could effectively check leaf folder damage revealing the 

possibility of combining neonicotinoids with synthetic pyrethroids for the management of both leaf folder 

and BPH and / or WBPH (DRR, 2001). 

Resurgence in Other Insect Pests 

Mani and Jayaraj (1976) reported resurgence of blue leafhopper, Zygina maculifrons (Motch) when acephate, 

dicrotophos, and monocrotophos were applied as seed and seedling root dip treatments. Lower contents 

of carbohydrates and calcium, and higher contents of nitrogen and phosphorus and narrow C: N ratio 

observed in treated plots were suggested to be responsible for resurgence of the insect. In Japan, 

insecticide induced resurgences of green leafhopper, Nephotettix cincticeps has been attributed to the 

destruction of natural enemies, particularly spiders (Kiritani et al., 1971; Kiritani, 1979). The populations 

of striped stem borer Chilo suppressalis Walker in many areas in Japan increased after large scale use 

of HCH and parathion until late 1960s (Miyashita, 1963). This was reported to be due to large scale 

destruction of trichogrammatid egg parasites, particularly Trichogramma japonicum Ashm (Nozoato and 

Kiritani, 1976). Apart from direct lethal effects, extermination of Naranga aenescens Moore, an alternate 

host of T. japonicum, during the absence of Chilo eggs in the rice fields seemed to be responsible for C. 

suppressalis resurgence (Iyatomi, 1951). 

Strategies to Overcome Resurgence of BPH 

The strategies described below, may be followed to minimize the insecticide-induced resurgence of 

BPH in rice ecosystem. 

Selection of Proper Insecticide(s) 

Among the insecticides evaluated in the national programme, those with high degree of toxicity to BPH 

and very low toxicity to natural enemies, particularly Cyrtorhinus spp, Microvelia sp. and spiders could be 

84


selected after testing, and recommended for BPH control. Krishnaiah and Kalode (1987) recognized 

that monocrotophos and phosphamidon (500g a.i./ha) as sprays could effectively check BPH build up. 

On the other hand, methyl parathion, fenvalerate, deltamethrin, chlorpyriphos, and quinalphos exhibited 

a tendency towards BPH resurgence. Further, spraying of a resurgence causing insecticide such as 

quinalphos in early stages of crop growth (upto 56 DAT), followed by monocrotophos spray (70 to 98 

DAT) could avert resurgence of BPH. Krishnaiah and Kalode (1993a) reported that ethofenprox (an 

ether derivative insecticide) @ 100 g a.i./ha sprayed at fortnightly intervals could successfully check 

BPH build up without adversely affecting mirid bug C. lividipennis and spiders, and produced grain yields 

similar to monocrotophos treatment. Under similar conditions, deltamethrin treated plots resulted in 

70% hopper burn (Table 13). Further, studies have shown that tank mixing of buprofezin (a growth 

regulator) @ 100 g.a.i./ha with deltamethrin (25 g a.i./ha) completely prevented the resurgence causing 

effect of the later and controlled BPH effectively (Krishnaiah et al., 1996). Further, the populations of 

mirid bug and spiders could be maintained favourably with a mixture of buprofezin + deltamethrin, 

similar to plots treated with buprofezin alone under field conditions (Table 14). 

Table 13 : Efficacy of Ethofenprox against BPH and safety to natural enemies under field conditions 

Insecticide 

Rate 

(g a.i./ha) 

BPHMB BPH / MB Spiders 

Hopper 

burn (%) 

Yield 

(t/ha) 

Ethofenprox 25 306ab 129a 3.1b 2.3a 2.9bc 3.4bc 

Ethofenprox 50 109bc 50ab 2.6b 2.8a 1.1bc 3.2c 

Ethofenprox 100 24cd 15b 1.6b 3.3a 0.8bc 4.6a 

Ethofenprox 200 15cd 20bc 1.0b 1.8a 0.6c 4.2ab 

Deltamethrin 50 1301a 1.5d 864.8a 1.8a 70.7a 0.7e 

Monocrotophos 500 24d 4.5cd 23.6b 2.8a 1.4bc 4.2ab 

Untreated control - 214ab 111a 1.9b 1.3a 11.4b 2.0d 

(Krishnaiah and kalode 1993a) 

Note: The values in a column followed by same letter are not significantly different at P=0.05 according 

to l.s.d method MB= mirid bug 

Among the most recent insecticides, the neonicotinoids like imidacloprid and thiamethoxam (25 g a.i./ 

ha) and phenyl pyrazoles like fipronil and ethiprole (50 g a.i./ha) were found to be highly effective against BPH 

and WBPH under glasshouse (Krishnaiah et al., 2004) and field conditions (DRR 1999-2003). 

Intensive field studies to utilize thiamethoxam and imidacloprid (25 g a.i./ha) in combination with synthetic 

pyrethroids like betacyfluthrin (12.5 g a.i./ha) were proved to be useful in the management of 

BPH and leaf folder similar to or better than monocrotophos (500 g a.i./ha) (Krishnaiah et al., 2003). 

The combination treatments although reduced the mirid bugs (MB), the predators of BPH in absolute 

numbers, maintained favourable BPH/MB ratio on par with untreated control. These results have been 

confirmed in coordinated experiments also (Krishnaiah et al., 2003) (Table 15). 

85


Table 14 : Influence of buprofezin in management of BPH resurgence due to synthetic pyrethroids 

Insecticide 

Cypermethrin 100 1710a 89.3a 18.8a 8.5a 5.61a 

Deltamethrin 50 1835a 91.0a 21.0a 9.0a 4.83b 

Buprofezin 

Cypermethrin + 

200 32c 48.5b 0.7b 4.5bc 4.16b 

Buprofezin 

Deltamethrin + 

100 +200 16c 32.8bc 0.5b 1.5d 5.88a 

Buprofezin 50 +200 17c 27.3c 0.7b 2.0cd 5.88a 

Monocrotophos 500 185b 96.3a 1.9b 6.0ab 4.50b 

Untreated control 154b 102.5a 1.3b 7.0ab 4.33b 

Dosage and Application Methods 

As discussed earlier dosage and method of application also influence the degree of resurgence. 

Therefore, it is necessary to recommend correct dosage of the effective insecticide. This is particularly 

important in case of BPH as it feeds at the basal portion of the plant, and is mostly sedentary. It seldom 

comes in contact with the insecticide sprayed. Application of high volume spray is drudgery and involves 

high cost. Therefore, farmers use too little spray fluid resulting in poor coverage. Pickin et. al. (1980) 

suggested that the deposition of insecticide at the feeding site of BPH with ULV application is very 

effective. They also reported that controlled droplet application technique could provide, effective 

control of BPH. Usually, insecticides applied as foliar sprays, when exposed in the field have residual 

toxicity for short period only. According to Mochida and Heinrichs (1983), micro-encapsulation of 

insecticides may provide means of slow release thus increasing residual toxicity. 

Botanical Insecticides 

Use of indigenous plant products such as neem oil will go a long way in overcoming the problem of 

resurgence. Krishnaiah and Kalode (1993b) reported that some of the neem formulations (Neemark, 

Nimbosol, Nimba (IARI), Neemta 2100, and Repelin) are effective against BPH under greenhouse conditions. 

It has also been documented that Neem oil at 1% and 4% concentrations does not cause resurgence of 

86 

Rate 

g a.i./ha 

BPH 

Mirid bugs/ 

10 hills 

BPH/MB 

BPH/MB 

83 DAT 83 DAT 83 DAT 83 DAT 

Spiders/ 

10 hills Yield 

(t/ha) 

(Krishnaiah et al., 1996) 

NB: Values in the same column followed by a common letter do not differ significantly at P = 0.05 

according to l.s.d method.


Table 15 : Efficacy of synthetic pyrethroid and neonicotinoid insecticides and their combinations against 

BPH, stem borer and leaf folder and safety to natural enemies under field conditions, wet season, 2001 

Insecticide 

Rate 

(g a.i./ha) 

BPH Mirid bugs 

(AN/10 h) (AN/10 h) 

BPH/MB 

(AN/10 h) 

Stem 

LFDL/10 h 

borer(%DH) 

61 DAT 61 DAT 61 DAT 51 DAT 75 DAT 

Yield 

(t/ha) 

Betacyfluthrin 12.5 2218d 335a 6.6d 7.5b 8a 1.8 

Thiamethoxam 25 64a 29d 2.2abc 4.4a 28bc 3.1 

Imidacloprid 25 47a 25d 2.0ab 7.4b 28bc 3.5 

Betacyfluthrin + 

Thiamethoxam 

12.5 + 25 64a 44d 1.9a 6.6ab 17ab 3.8 

Betacyfluthrin + 

Imidacloprid 

12.5 + 25 290b 87c 3.2bc 5.2ab 22b 3.7 

Monocrotophos 500 294b 103c 2.9abc 6.0ab 17ab 3.5 

Untreated Control 684c 212b 3.3c 17.4c 39c 3.2 

(Krishnaiah et. al. 2003) 

AN = Average number, DAT = Days after transplantation, BPH = Brown planthopper, DH = Dead hearts, 

NB: All the insecticide treatments were given at 34, 45, 54 and 66 DAT. 

The values in a column followed by the same letter are not significantly different at P=0.05 according to 

l. s.d method. 

BPH when there was a complete hopper burn in deltamethrin treated plants (Krishnaiah and Kalode, 

1992). 

Further intensive field studies revealed that the neem formulations viz., Neemgold and Nimbecidine 

which are oil based with low azadirachtin content (300 ppm) when used at 4% concentration (12 ppm 

azadirachtin) prevented the resurgence of BPH caused by synthetic pyrethroid deltamethrin (25 g a.i. / 

ha) as tank mix before spraying, or as alternate applications with deltamethrin. However, Neem Azal T/S 

having 10,000 ppm azadirachtin at 0.5% concentrations (50 ppm of azadirachtin) could not prevent 

resurgence of BPH caused by deltamethrin in similar applications (Krishnaiah et al., 2000). Thus, 

suggesting that the constituents other than azadirachtin present in oil based neem formulations appeared 

to be responsible for preventing resurgence of BPH caused by deltamethrin under field conditions in rice. 

Resistant Varieties 

Resistant varieties have tremendous capacity to lower the degree of resurgence. Therefore, these 

must be propagated for cultivation in large areas to keep the BPH problem under check. However, the 

87


problem of biotypes needs to be considered and sequential release of varieties must be followed to keep 

pace with the development of biotypes. This appears to be a practical and sound way of overcoming the 

resurgence problem. 

Insecticide Resistance 

Development of insecticide resistance in BPH against the commonly used insecticides could lead to 

resurgence. Therefore, continuous monitoring of the field populations for their level of insecticide resistance 

is a practical necessity. Careful selection of alternatives from among the available insecticides must be 

based on cross resistance pattern of the local populations to insecticides. 

88


BOTANICAL INSECTICIDES IN RICE 

PEST MANAGEMENT 

Farmers in oriental region were using simple plant products such as pyrethrum, derris, tobacco and neem 

for controlling insect pests prior to the introduction of synthetic pesticides. Neem leaves were mixed with 

grain before storage to protect from insect pests. The development of the concept of integrated pest 

management and environmental concern among scientists, administrators and general public led to renewed 

emphasis on utilization of plant products particularly neem in pest management. Neem, Azadiracta indica 

A. Juss. is grown extensively in tropical and subtropical regions of the world. Every part of the plant is 

bitter but maximum concentration of bitter is present in seed. Neem oil, which is expelled from decorticated 

neem seed by mechanical means and the remaining solid residue called neem cake have been extensively 

tested for finding their efficiency in controlling rice pests. Other plant species such as pinnai (Calophyllum 

inophyllum) and mahua (Madhuca longifolia var latifolia) have also undergone a limited testing. Greenhouse 

studies have been conducted on the effect of botanicals on repellency, feeding inhibition, growth, 

metamorphosis disruption, oviposition and egg hatchability and followed by field investigation. Of late 

some commercial neem formulations are also available (Table 16). 

Table 16 : Details of some commercially exploited neem formulations 

Neem formulation Azadirachtin Conc. (ppm) Source 

Achook 300 M/s. Godrej Agrovet Ltd, 

Chennai - 600098. 

Neemax 300 M/s. Ecomax Agrosystems, 

Hyderabad - 500 029 

Nimbicidine 300 M/s. T. StaRes & Co. Ltd, 

Coimbatore-641 018 

Neemgold / 300 M/s. SPIC Bioproducts, 

Neemgold 4 Chennai - 600 116. 

Rakshak 1500 Murkumbi Manufacturing, 

Belgaum - 590 002. 

Fortune Aza 1500 M/s. Fortune Biotech Ltd, 

Secunderabad - 500 380. 

Econeem 3000 M/s. P. J. Margo Pvt. Ltd, 

Bangalore - 560 058. 

Neem Azal TIS 10000 M/s. E.LD. Parry (India) Ltd, 

Chennai - 600001. 

89


GREENHOUSE STUDIES 

Orientation and settling behaviour 

Neem oil possesses a strong repellance activity to brown planthopper (BPH). Only a very low number of 

BPH settled on treated plants. Even at 3% concentration of oil, the spray treated plants attracted not 

more than 36% of insects (Saxena et al., 1980a). There was a progressive decrease in arrivals of BPH 

and WBPH to treated plants with an increase in concentrations of neem oil. When neem oil treated leaves 

were offered to leaf folder in a choice test, it significantly lowered the number of larvae that arrived on 

treated leaves, particularly at 12% or higher concentration (Saxena et al., 1980b). However, similar 

effects were not observed in case of green leafhopper females (Heyde et al., 1983). 

In a comparative study (Krishnaiah and Kalode 1988b), with other non-edible oils, neem oil and pinnai oil 

applied as spray exhibited more or less similar repellency to BPH adults while mahua oil was inferior. 

However, neem cake applied to soil did not restrain BPH settling response on TN 1 in a choice test. 

(Saxena et al., 1984). The soil applied neem cake might not have released sufficient voaltiles to show 

repellency to insects arriving on leaves. 

Feeding behaviour 

Feeding deterrency of neem oil was observed in many insect pests. On treated plants, BPH adults were 

restless, took longer time to locate feeding sites and ingested smaller quantities of food. Such effects 

were not observed in vegetable oil treated plants (Saxena et al., 1980a). Significant reduction in quantity 

of food ingested by BPH, WBPH and GLH occurred even at 1% concentration of neem oil (Heyde et al., 

1983). Custard apple oil was relatively more effective as antifeedant than neem oil against BPH, WBPH 

and GLH (Saxena et al., 1983). Among others, pinnai and mahua oils were comparable to neem oil in 

reducing BPH feeding as indicated by significantly less honeydew excretion on TN 1 plants even at 3% 

concentration (Krishnaiah and Kalode, 1988b). Reduced phloem feeding increased xylem feeding, repeated 

probing and profuse salivation of Nephotettix virescens on plants sprayed with 10% neem oil was 

demonstrated by Saxena and Khan (1985). 

Significant reduction in duration of phloem feeding by GLH was observed with neem seed bitters (NSB) at 

2500 ppm (Kareem et al., 1988). On neem oil (50%) treated plants feeding duration in BPH also was 

decreased to 6 min. in contrast to 53 min in control (Rajasekharan et al., 1987). 

Antifeedant activity of neem oil against leaf folder was higher with an increase in concentration of neem 

oil spray on plants, as measured by quantum of excreta. However, even neem oil spray at 25% was 

similar to control when treated plants were exposed to 2 to 4 days light (Saxena et al., 1980b). Reduced 

feeding period of leaf folder on NSB treated leaf cuts was shown by Kareem et al., (1988). 

90

Gr Growth Gr wth and and metamor metamorphosis 

metamor phosis 

EFFECT EFFECT OF OF NEEM NEEM OIL OIL AND AND O OOTHER 

O THER OILS 

OILS 


In case of leaf- and planthoppers, disruption of growth was mainly assessed in terms of proportion of 

first instar nymphs reaching adult stage. While in case of lepidopterous insects irregularities in the form 

of larval and pupal intermediaries were observed. 

On plants treated with neem oil at 3%, only 3 to 9% of BPH nymphs became adults as compared to 67 to 

88% reaching adult stage in relatively shorter periods in untreated control (Saxena et al., 1980a). 

Similarly, neem oil retarted the growth and development of first instar WBPH and GLH nymphs also. Only 

12% of WBPH and 2% of GLH nymphs became adults (Heyde et al., 1983) at 3% concentration. Among 

other oils, custard apple oil was more toxic to BPH, WBPH and GLH than chinaberry oil and neem oil 

(Saxena et al., 1983). 

Mahua and pinnai oils exhibited more toxicity to BPH than maravetty (Hydnocarpus weightiana) oil. In 

further studies, pinnai oil was similar to neem oil in affecting the growth of first instar nymphs of BPH and 

GLH while mahua oil was inferior. However, an oil concentration of 6% was required to obtain a considerable 

adverse effect on the growth of these homopetrans (Krishnaiah and Kalode, 1988b). 

Regarding lepidopteran insects, confinement of 5th instar leaf folder (Cnaphalocrocis medinalis) larvae to 

cut leaves treated with 12% or more neem oil resulted in pronounced aberrations in behaviour and form, 

and enhanced mortality during metamorphosis (Saxena et al., 1980b). Some larvae became dark in 

colour, while others failed to fold leaves or developed into larval-pupal intermediaries. 

EFFECT OF NEEM SEED BITTERS 

When neem seed kernel water extract (neem bitters) was dried at low temperatures and used as an 

aqueous spray at 2500 to 10,000 ppm, it completely inhibited the growth of BPH and GLH (Kareem et al., 

1987). Krishnaiah and Kalode (1988b) found neem seed bitters to be more effective as seedling root dip 

than as spray. Green leafhopper was more susceptible to neem seed kernel water extract than BPH as 

spray as well as root dip treatments. Although neem seed bitters, as a formulation appeared to be far 

superior to oils, production in bulk quantities pose problems (Table 17). 

EFFECT OF COMMERCIAL NEEM FORMULATIONS 

When commercial neem formulations such as Neemax, Neemgold, Rakshak, Neem Azal T/S, were evaluated 

against BPH nymphs for their direct toxicity and LC 50 values were calculated, the results clearly indicated 

that the oil based neem formulations with lower azadirachtin content (300 ppm) exhibited relatively lower 

toxicity than formulations with higher azadirachtin content on formulation basis. But, when assessed 

based on azadirachtin concentration, the oil based formulations exhibited relatively higher toxicity. This 

showed that constituents other than azadirachtin are also playing role in exercising toxic effect against 

BPH (Table 18) (Krishnaiah, 2000). 

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Table 17 : Effect of neem bitters (neem seed kernel water extract) on nymphal survival 

of brown planthopper (BPH) and green leafhoppers (GLH) 

Neem bitters 

concentration (ppm) 

100 95a 80a 65b 58b 

500 83ab 42b 20c 0c 

2,500 40c 0c 0d 0c 

5,000 1d 0c 0d 0c 

10,000 0d 0c 0d 0c 

0 (Control) 84ab 87a 84a 68a 

EFFECT OF RICIN FROM CASTOR 

Kwon et. al. (1991) from Korea republic observed high insecticidal activity of ricin (a compound isolated 

from castor leaves and identified as 1,2-dihydro-4-methyl-2-oxo-3-pyridine carbonitrile) to BPH. 

92 

Brown planthoppers Green leafhoppers 

Spray Root dip Spray Root dip 

Figures in a column followed by common letter are not significantly different at P = 0.05; 

(Krishnaiah and Kalode, 1988b) 

Table 18 : Relative Efficacy of neem formulations against BPH 

Neem formulations LC 50 (% Conc.) 

Azadirachtin Conc. 

(ppm) in formulation 

LC 50 as Conc. Of 

Azadirachtin (ppm) 

Nimbecidine* 1.695 300 5.09 

Neem Azal T/S 0.962 10000 96.16 

Econeem 2.114 3000 63.42 

Neemgold 4* 0.529 300 1.59 

Fortune Aza 0.973 1500 14.59 

Rakshak 1.454 1500 21.81 

Achook* 1.317 300 3.95 

Neemax* 0.854 300 2.56 

* oil based neem formulations 

(Krishnaiah, 2000)

Oviposition and egg sterility 


Earlier studies indicated that oviposition by BPH was deterred when gravid females were confined to 

plants treated with 12% or higher concentration of neem oil (Saxena et al., 1980a). But there was no 

significant difference between 12 and 100% neem oil concentrations (Kalode and Krishnaiah, 1987). 

Similarly, some differences in fecundity and egg hatchability of BPH were observed in studies at IRRI. But 

studies at DRR showed that such differences among concentrations were not significant in case of BPH 

and GLH (Kalode and Krishnaiah 1987). When roots of 7 day old TN 1 seedlings were soaked in 5% 

neem seed kernel extract (NSKE) and 1% urea for 3 to 24 h, and GLH were allowed to oviposit, the 

number of eggs deposited were significantly less than water but higher than urea treated controls (Kareem 

et al., 1988). The results obtained in such studies therefore, showed no consistency on the effect of 

NSKE on oviposition of GLH. 

Dipping the eggs of leaf folder, C. medinalis in neem oil (at 12, 25 and 50% concentration) largely 

prevented the emergence of first instar larvae (Saxena et al., 1980b). Such inhibitory action most 

probably was caused by a choking effect of the oil but not by growth regulating properties of the ingredients 

(Schmutterer 1990). 

Behaviour of exposed insects 

In homopterous insects, such as BPH, WBPH and GLH, the longevity was adversely affected by application 

of neem derivatives. Insect survival was greatly reduced when caged in pairs on plants treated with neem 

oil at 6% or higher concentrations. The pre-ovipositional period of BPH, WBPH and GLH was prolonged by 

2 to 8 days at higher levels of neem oil, there by considerably reducing effective oviposition period 

(Heyde et al., 1983). Females of BPH topically treated with 2.5 to 5.0 mg neem oil per insect or caged on 

plants sprayed with 3% neem oil, failed to produce normal courtship signals. At higher concentrations, 

most females did not emit signals and therefore, males could not locate them (Saxena et al., 1989; 

Schmutterer 1990). 

SYSTEMIC ACTION OF NEEM FORMULATIONS IN RICE 

Studies on systemic action of Neem Azal T/S and Rakshak revealed that following application through 

foliar sprays and seedling root dip, the rice seedlings showed significantly high mortality of BPH, WBPH 

and GLH confined to untreated portions of the plant thereby confirming downward and upward translocation 

of active principles in neem formulation. Results also showed that 6 hours was the optimum period for 

seedling root dip with Neem Azal T/S for getting good mortality of GLH (Table 19) (Krishnaiah, 2000). 

FIELD EVALUATION 

In India, neem oil was evaluated against insect pests attacking rice fields as early as 1978 in comparison 

93


with synthetic insecticides such as quinalphos, phosalone, chlorpyriphos, monocrotophos, etc. (Krishnaiah 

and Kalode 1984). At IRRI, field evaluation of neem oil was initiated in 1978. Incidence of ragged stunt 

virus (RGSV) disease transmitted by BPH was significantly reduced with 12% ultra low volume (ULV 5 to 

10 l/ha spray fluid) spray of neem oil, applied five times at an interval of 20 days (Saxena et al., 1980a). 

Application of 120 kg N/ha as a mixture of neem cake and urea (3: 10) generally lowered the incidence 

of grassy stunt virus and its vector BPH, and tungro virus. However, other pests such as whorl maggot, 

stem borer and gundhi bug were not affected by neem cake. The plots treated with neem cake yielded 

significantly more than control. However, this might partly be due to a more efficient utilization of applied 

nitrogen through a reduction in nitrification by neem cake than through any pest control properties of the 

material. 

In China, basal application of neem cake (150 kg/ha) followed by 2% neem oil and custard apple oil spray 

(4 l/ha) resulted in a moderate control of planthoppers, N. lugens, S. furcifera and leaf folder, C. medinalis 

(Chiu et al., 1988). Green leafhopper population was significantly lowered by a mixture of 2% neem oil 

and custard apple oil (4:1) when applied at 10 day interval in Philippines (Atienza et al., 1988). A mixture 

of 50% neem oil and custard apple oil (4:1) alone (6 l/ha) or in combination with a basal application of 

neem cake, checked white head incidence (Kareen et al., 1987). In India, low volume (LV – 50 to 100 l/ 

ha spray fluid) spray of 10% neem oil at 10, 30, 45 and 60 days after transplanting in Tamil Nadu 

significantly reduced white ear head (stem borer) damage to 2.8% as against 6.5% in control (Murugesan 

et al., 1987). However, a high volume application (500 to 1000 l/ha) of 2% neem oil or a ULV application 

of 50% neem oil was ineffective against stem borers. High volume application of 1% or 3% neem oil or 

LV application of 5% or 10% neem oil reduced both BPH population and leaf folder damage, equal to 

monocrotophos. These treatments were superior to ULV (Rajasekaran et al., 1987). 

Basal application of neem cake (100 kg/ha) followed by neem oil spray at 10 and 30 days after planting 

proved effective against stem borers (Samalo, 1988). A second round of spray application coinciding 

with moth emergence was considered as deterrent for oviposition and there by resulting in less larval 

damage. However, studies at DRR showed that neem treatments were not as effective as monocrotophos 

94 

Table 19 : Upward translocation of active principles in neem formulations 

when given as seedling root dip 

Treatment 

2 

% Mortality of GLH (at days after exposure) 

3 4 5 7 

Neem Azal T/S 200 ppm 13b 44b 56b 62b 66b 

Neem Azal T/S 300 ppm 21b 46b 59b 60b 61b 

Rakshak 100 ppm 20b 42b 50b 55b 60b 

Control 0a 0a 0a 0a 0.8a 

Note: Figures in a column followed by same letter are not significantly different at 5% according to lsd


against dead heart damage caused by stem borers. As ULV, neem oil along with neem cake as basal 

application gave grain yields lower than monocrotophos (Kalode and Krishnaiah 1987). Similar superiority 

of monocrotophos over neem oil was reported from Punjab also (Jaswant Singh et al., 1990). 

INEFFECTIVENESS OF NEEM PRODUCTS AGAINST GALL MIDGE 

Gall midge incidence was lowered in Orissa, from 27% in untreated control to 20% in neem cake-urea 

mixture (1:3 w/w) treated plots at 75 kg N/ha. However, the differences were not significant (Panda,1987). 

In another study (Samalo, 1988) from Orissa, neem cake (100 kg/ha) and 3% neem oil spray recorded 

a slightly less incidence of gall midge (21.2% to 21.5% silver shoots). In Chattisgarh, neem oil spray at 

4% as high volume was ineffective against gall midge (Shukla et al., 1987). These results showed that 

neem products are more or less ineffective against gall midge under field conditions. 

LOW EFFICACY OF NEEM PRODUCTS IN MULTIPEST SITUATIONS 

Green leafhopper population and tungro virus infection were significantly reduced in plots planted with 

seedlings treated with neem bitters followed by weekly foliar sprays at 2500 ppm, but was not comparable 

to monocrotophos (0.75 kg a.i./ha) (Kareem et al., 1988). Basal application of neem cake (150 kg/ha) 

followed by 3% spray of oils (neem, mahua, pinnai or neem seed kernel suspension) were inferior 

(Krishnaiah and Kalode, 1988b) to monocrotophos (0.50 kg a.i./ha) in checking leaf folder damage. 

Shukla and Kaushik (1994) observed in a field experiment that NSKE (5%) resulted in 80% reduction in 

population of WBPH in kharif compared to 53% reduction in rabi. Neem oil (3%) could reduce 77% and 

32% respectively as compared to 91% and 66% in case of monocrotophos (0.5 kg a.i./ha). Korat et al., 

(1999a) evaluated the commercial neem formulations with different levels of azadirachtin like, Nimbicidine, 

Neemax, Neem Gold, Econeem, Neem Azal T/S and Fortune-Aza and compared with chlorpyriphos. They 

observed that these formulations were as good as chlorpyriphos against leaf folder, stem borer and 

WBPH. Sudhakar (2000) from Rajendranagar observed that Neemorate, a granular neem formulation @ 

20kg /ha was more effective against stem borer, gall midge, whorl maggot and thrips, compared to two 

spray formulations of neem viz. Repelin and Neemax. The effectiveness of all the formulations increased 

when combined with chlorpyriphos. 

SAFETY TO NATURAL ENEMIES 

CRUDE FORMULATIONS OF NEEM 

Botanicals such as neem oil, neem cake and other non-edible oils and cakes are considered to be safer to 

natural enemies than synthetic insecticides. 

Predators of leaf and planthoppers such as spiders, particularly Lycosa pseudoannulata and mirid bug, 

Cyrtorhinus lividipennis were found unaffected by neem cake and urea (3:10) application to rice fields at 

IRRI (Saxena et al., 1984). Neem oil (10 l/ha) as a high volume spray emulsified with detergent registered 

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marginally higher population of mirid bug (Krishnaiah and Kalode 1984). In China, basal application of 

neem cake (150 kg/ha) followed by 2% neem oil and custard apple oil mixture (150 l/ha) was reported 

to be safe for Lycosa as well as egg parasite, Trichogramma (Chiu et al., 1988). In the Philippines, plots 

planted with seedlings systematically treated with neem seed bitters followed by weekly foliar spray 

maintained predatory mirid bug and spider populations similar to untreated check, while monocrotophos 

(0.75 kg a.i./ha) significantly lowered the natural enemies (Kareem et al., 1988). Raguraman and 

Rajasekharan (1996) observed better colonization of predatory wolf spider, Lycosa pseudoannulata in 

neem treatments like NO, NSKE, and neemcake extract compared to monocrotophos. Dash et al., (2001) 

also reported better recolonization of all the predatory spider populations viz. Lycosa pseudoannulata, 

Tetragnatha maxillosa, and Argiope catenulata and mirid bugs, Cyrtorhinus lividipennis. 

COMMERCIAL FORMULATIONS OF NEEM 

Experiments on safety of neem formulations to velid predator, Microvelia douglasi atrolineata showed that 

Neemax and Rakshak were the safest neem formulations followed by Fortune Aza. Studies on safety of 

neem formulations to mirid bug Cyrtorhinus lividipennis revealed that Neemgold at 0.5% and Neemax at 

2% were the safest while 100% mortality was recorded in insecticide treatments (Jhansi Lakshmi et. al. 

1998). Laboratory tests on the safety of neem formulations to egg parasite Trichogramma japonicum 

revealed that % parasitization as well as emergence of adults was affected to a lower degree by neem 

Table 20 : Potential toxicity of neem formulations to Trichogramma japonicum 

Neem fomulation 

Neemax 300 ppm 40 64.8e 100.0a 38.3h 83.4e 

Achook 300 ppm 40 56.9e 73.8bc 47.5e 100.0a 

FortuneAza 500ppm 5 74.4cd 48.9de 53.5fg 92.0c 

Neem Azal T/S 10000 ppm 5 60.6e 52.0e 66.1ncde 86.8de 

Econeem 3000 ppm 5 75.4c 100.0a 57.5ef 100.0a 

Neem gold 300 ppm 5 42.9fg 28.1f 7.2mn 57.8hi 

Rakshak 1500 ppm 5 76.1c 86.6abc 24.4jkl 30.3k 

NG-4 300 ppm 2 47.9f 24.5g 

Nimbicidine 300ppm 6.0i 16.0g 24.6kjl 32.9k 

96 

Dosage 

(g or ml / l) 

Treatment one day 

after releasing for 

parasitization 

Parasitism 

(%) 

Adult emergence 

(%) 

T. japonicum 

Treatment before 

releasing for 

parasitization 

Parasitism 

(%) 

Adult emergence 

(%) 

(Jhansi Lakshmi et. al. 1997 b)


formulations (Table 20) than insecticides like quinalphos and chlorpyriphos (Jhansi Lakshmi et al., 1997b). 

When eight neem formulations were tested in the greenhouse against the veliid predator, Microvelia 

douglasi, it was found that Neemax and Rakshak were the safest neem formulations followed by Fortune 

Aza and Econeem at lower dosage whereas Neem Azal, Neemgold, NG4 treatments resulted in high 

mortality of Microvelia (Jhansi Lakshmi et al., 1997a) (Table 21). 

Table 21 : Potential toxicity of neem formulations to C. lividipennis and M. atrolineata 

Neem fomulation / Insecticide Dosage 

(g or ml / l) 

C. lividipennis M. atrolineata 

Percent mortality after 

24h 48h 72h 1h 24h 

Neemax 300 ppm 40 13.3cd 43.3ab 56.7b 2(3.7) 4(7.4) 

Achook 300 ppm 40 53.3b 93.3a 100.0a 0(0) 30(32.9) 

FortuneAza 500ppm 5 0(0) 10(16.4) 

Neem Azal T/S 10000 ppm 5 20.0c 43.3ab 63.3abd 6(8.9) 100(89.9) 

Econeem 3000 ppm 5 16.7cd 76.7ab 83.3ab 0(0) 34(32.4) 

Neem gold 300 ppm 5 43.3b 53.3ab 90.0a 2(3.7) 100(89.9) 

Rakshak 1500 ppm 5 0(0) 2(3.7) 

NG-4 300 ppm 2 36.7bc 83.3a 90.0a 10(16.4) 90(73.6) 

Neem oil 40 100(89.9) 100(89.9) 

Neem Seed Kernel Extract 2 2(3.7) 76(61.2) 

quinalphos 25EC 2 10(14.3) 100(89.9) 

Chlorpyriphos 20EC 2.5 100a 100a 100a 100(89.9) 100(89.9) 

Monocrotophos 36 WSC 1.5 100a 100a 100a 40(39.2) 60(50.8) 

Carbofuran 3 G 60 16(20.7) 84(69.3) 

Phorate 10 G 20 0(0) 6(11.5) 

lsd 0.05 12.24 16.8 

Note: figures in a column followed by same letter are not significantly different at 0.05% level as per DMRT 

(Jhansi Lakshmi et. al. 1997 a) 

DISEASE TRANSMISSION 

In greenhouse studies, neem oil was highly effective in a concentration dependent manner in reducing the 

survival of BPH and in suppressing transmission of both grassy stunt and ragged stunt viral diseases 

(Saxena and Khan, 1985). Neem oil and custard apple oil when sprayed at 5, 10, 20, 30 or 50% 

concentration significantly reduced GLH survival and tungro virus transmission as compared to Teepol 

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(liquid detergent) 0.1%. The insects failed to survive and transmit tungro to plants sprayed with oil 

beyond 3 days of exposure, while in control, the insects survived for 20 days and transmitted tungro for 

5 days (Mariappan and Saxena, 1983). Further, a synergistic effect of the neem oil and custard apple oil 

was also observed. Even at 5% concentration, a mixture of neem oil and custard apple oil (4:1) was as 

effective as 20% custard apple oil in reducing GLH survival and transmission of tungro (Mariappan and 

Saxena, 1984). Both survival of GLH and tungro virus transmission were significantly reduced by soil 

treatment with neem cake and mahua cake (200 kg/ha). Sprays with neem cake extracts (5%), mahua 

cake extract (5%), neem bitters (2%) and Repelin (2%) significantly lowered GLH survival and tungro 

transmission at Coimbatore (Gurubasavaraj et. al, 1988). In Bangladesh, neem oil (3%) was superior to 

NSKE (5%) and neem cake in reducing GLH populations and reducing RTD incidence (Karim, 1999). In 

another field trial, lowest population of GLH vector and lowest RTD incidence were observed in plots 

treated with neem cake @ 5 kg / 0.032 ha of nursery followed by foliar spray of NSKE (5%) (Rajappan et 

al., 2000). Considerable reduction in populations of GLH and tungro infection was reported in plots 

treated with neem seed bitters before transplanting followed by spraying with 10,000 ppm neem seed 

bitters at two week intervals after transplanting (Saxena et al., 1988). Rajappan et al., (1999) observed 

reduction in rice yellow dwarf disease (RYD) transmitted by GLH, following the application of neem and 

pungamia oils but to a lower level compared to insecticide monocrotophos. 

EFFECT ON LEAF FOLDER AND STEM BORER 

Leaf folder appeared to be more sensitive to neem products compared to stem borer. Rajasekharan et 

al., (1987) observed considerable reduction in damage caused by leaf folder larvae under field conditions 

followed by application of seed oils of mahua (Bassia latifolia), maravetty (Hydnocarpus wightiana) and 

pinnai (Calophyllum inophyllum). Mayabini Jena (1997) reported that neem bark decoction was very 

effective in reducing feeding and rate of pupation of leaf folder compared to neem oil, neem leaf extract 

and leaf decoction. Dhaliwal et al., (2002) reported high potency of neem based commercial formulations 

viz. Rakshak (1%), Neem Azal (5%) in reducing the damage by leaf folder and stem borer under field 

conditions. Zhu et al. (2004) from China studied the biological activity of azadirachtin, the active principal 

in neem against Chilo suppressalis, and observed that the mortality of newly hatched larvae was 100% 

within 24 hours after treatment following the application at 6, 3, and 2 mg azadirachtin per litre of spray. 

DEVELOPMENT AND TESTING OF NEW FORMULATIONS OF NEEM 

Considerable effort was put in the development of formulations from neem at Indian Agricultural Research 

Institute, New Delhi and consequently neem powder; an emulsion and a solution were developed. Neem 

powder, when mixed with wheat flour and tested against Tribolium castaneum and Corcyra cephalonica, at 

2% concentration, inhibited the development of larvae to adults. Neem emulsion exhibited LC 50 of 

0.328% against the aphid, Lipaphis erysimi Kalt. Neem solution completely inhibited the development of 

BPH nymphs at a concentration of 0.1 to 0.3% (Singh 1988). At IRRI, a water soluble neem formulation 

98


called neem seed bitters (NSB), with systemic property, was developed by extraction of neem seed 

kernels with water followed by freeze drying. NSB has been tested against both leaf and planthoppers of 

rice extensively in greenhouse and field trials at many research centres (Saxena et al., 1987; Kareem et 

al., 1988; Krishnaiah and Kalode 1988b). Considering the advantages of using botanicals, a number of 

private organizations have developed ready to use formulations of botanical pesticides. Such private 

sector research has resulted in the development of product; RD-9 (Repelin, Indian Tobacco Company 

Ltd.) by taking commonly used safe plant materials available locally such as neem (Azadiracta indica), 

karanjia (Pongamia glabra), castor (Ricinus communis), mahua (Madhuca longifolia var. latifolia) and 

gingelly (Sesamum indicaum). Repelin acts as a repellent and antifeedant. Similarly other formulations 

such as Wellgro, Neemta 2100, Neemark, Neem Guard, have been developed by different companies. The 

National Chemical Laboratory, Pune developed two formulations called Margoside C.K and Margoside O.K. 

Our recent greenhouse evaluation demonstrated excellent growth inhibiting property of Margoside C.K 

against green leafhopper. Later on, a number of other private concerns started manufacturing the neem 

formulations like Neemax, Neemgold, Nimbicidine, Neemazal T/S, etc. with varying azadirachtin contents 

(Table1) (Krishnaiah, 2000). 

PRACTICAL PROBLEMS WITH BOTANICALS 

l Under field conditions, botanicals showed limited persistence. Temperature, ultraviolet light, pH of the 

treated surface, rainfall and other environmental factors may degrade active principals. Therefore, 

the residual life of botanical is around 3 to 5 days. This short residual period necessitates more 

frequent applications of botanicals as compared to insecticides, which are generally persistent for 7 – 

10 days. 

l Generally farmers are accustomed to quick knockdown effects of pesticides. Therefore, they may not 

be satisfied with usual slow action of botanicals. There is a need to educate farmers and create 

awareness on the special antifeedant effects of these materials. 

l Rains following foliar spray application may wash off the plant products before they reach the targets 

of actions. Therefore, these are likely to show better effectiveness during dry season. Botanicals are 

also normally less effective than synthetic pesticides. However, this should not cause concern because 

the natural enemies, which are often spared by botanicals, may take care of any remaining population 

of pest species. 

l Generally, adult insects, such as bugs and beetles are not killed by botanicals, but their fecundity is 

reduced. Therefore, the population in the next generation is expected to be well below economic 

threshold level with adult populations of rice hispa, leaf hoppers and planthoppers, the damage 

continues to occur even after application of botanicals. 

l Except certain formulations like neem seed bitters, botanicals in general are not systemic. Therefore, 

care should be taken for thorough coverage of plant surface when they are used as sprays. 

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ADVANTAGES OF PLANT PRODUCTS 

l As botanicals are primarily feeding poisons for nymphs and larvae of phytophagous insects, they 

show considerable selectivity towards natural enemies particularly parasitoids and predators. 

Therefore, these can be integrated with other control tactics in integrated pest management. 

l Botanicals are in general compatible with other bio-products such as microbial insecticides. 

l Farmers of Asia and Africa, who are generally poor, can benefit greatly, if they can be educated 

about proper utilization of botanicals available in these continents in great abundance. 

l Continued and persistent research on identification of active principles of botanicals would go a 

long way in synthesizing new groups of pesticides which may be environmentally safe and possess 

effectiveness for reasonable period. 

l The relatively shorter duration of persistence of botanicals under field conditions may not yield 

the desired short-term economic gains. But the use of botanicals will prevent secondary pest 

out-breaks, a common feature associated with synthetic insecticide application. 

l Synthetic pesticides with single active principle are likely to induce the development of resistance 

in insects. Botanicals on the other hand contain complex array of compounds with multiple effects 

and are unlikely to lead to pesticide resistance. Therefore, wherever possible, botanicals can be 

alternated with synthetic pesticides to hinder the development of insecticide resistance. 

100


BIO-PESTICIDES AND THEIR USE IN RICE IPM 

Biopesticides (also known as biological pesticides) are certain types of pesticides derived from such 

natural materials as animals, plants, bacteria and certain materials. For example, garlic, mint and baking 

soda all have pesticidal applications and are considered as biopesticides. There are approximately 175 

registered biopesticide active ingredients and 700 products. Biopesticides fall into three major categories. 

1) microbial pesticides 2) plant pesticides and 3) biochemical pesticides. Microbial pesticides contain a 

microorganism (bacterium, fungus, virus, protozoan, algae or nematode). The most widely known microbial 

pesticides are varieties of the bacterium Bacillus thuringiensis or Bt, which can control certain insects in 

some crops. Bt produces a protein that is harmful to specific insect pests. Certain other microbial pesticides 

act by out-competing pest organisms. Microbial pesticides need to be continuously monitored to ensure 

that they do not become capable of harming non-target organisms including humans. These biopesticides 

are less harmful than conventional pesticides, specific to the target organism, safe to non-target organisms, 

effective in small quantities, decompose quickly, do not cause environmental pollution, and can be used as 

alternatives to conventional pesticides. 

Fungal pathogens against rice pests 

Rice crop ecosystem provides a favorable environment for the exploitation of fungi as mycoinsecticides; 

but sufficient efforts were not put in for exploiting this potential in rice pest management. The major mycopesticides 

that have been attempted for the management of rice insect pests include the entomopathogenic 

fungi Beauveria bassiana and Metarhyzium anisopliae, which are pathogenic to leafhoppers and 

planthoppers. Gillespie et al., (1990) outlined a rational programme of strain selection for exploitation of 

the potential of these entomo-pathogenic fungi from the two major homopteran pests viz. Nephotettix 

virescens and Nilaparvata lugens. Feng and Johnson (1990) observed that two isolates of B.bassiana 

derived from N. lugens were less virulent to the aphid pest Diuraphis noxia compared to the isolate 

derived from Schizaphis graminum, indicating the host specificity among the isolates with in the same 

species of the fungus. Aguda et al., (1988a &b) observed that B.bassiana and M.anisopliae were infective 

to BPH in Philippines at a concentration of 102 to 108 conidia/ml under green house conditions at 15- 

300 C. 

The fungus Beauveria bassiana has wide host range and has been observed to be infecting other rice 

pests like rice hispa, Dicladispa armigera in Assam, India (Hazarika and Puzari (1990). Garcia et. al. 

(1990a) from Cuba observed both B.bassiana and M. anisopliae to be infective to rice pest, Sogatodes 

orizicola. Conidial suspensions of M.anisopliae were also pathogenic to Japanese root weevil, 

Lissorhopterous brevirostris (Garcia et al., 1990b). 

Factors affecting pathogenecity of fungi 

Among the factors that affect the pathogenecity of these fungi, maximum infection of the fungus, M. 

anisopliae was observed at a temperature of 25 0 C, 100% RH, and PH 7.0. against small brown planthopper, 

101


L. strietella (Lee and Hou 1989). The spore concentration of the fungus required for 50% infectivity to 

L.strietella was 2.57*105 conidia/ml. Among the agrochemicals that affect the pathogenicity of the fungus, 

M.anisopliae, the fungicides, benomyl and edifenphos and the insecticide carbaryl inhibited the germination 

of the conidia of the fungus while the insecticide buprofezin did not affect the infectivity of M. anisopliae 

(Aguda et al.,1988a; Lee and Hou, 1989). 

Preliminary studies were conducted on pathogenecity of the fungus, Fusarium palledoroseum towards 

leaf folder Cnaphalocrocis medinalis and observed that LD 50 concentration was 5.49*103 conidia/ml of 

the suspension by larval dipping method (Mnisegarane et al., 1997). 

Evaluation of Bt formulations 

Many commercial Bt formulations have been evaluated for their effectiveness against mainly leaf folder 

and sometimes against stem borers. Rath (1997) studied the effectiveness of four B.t. formulations 

against rice yellow stem borer and observed that BTK II and Dipel 3.5% were more effective than the 

other two formulations viz. Delfin 85% and Biolep. Roshan Lal (2001) also evaluated four B.t. formulations 

of var. kurstaki viz. BTKII, Delfin, Dipel and Biolep at 2000 g of formulation /ha and compared their 

effectiveness with insecticides against leaf folder and yellow stem borer under field conditions in Haryana, 

India. These were as effective as chlorpyriphos @ 250 g a.i./ha. Panda et al., (1999) from Orissa, India 

also observed that Bioasp, Biolep, Biotox, Dipel, and Delfin @ 2000 g of formulation /ha were highly 

effective against leaf folder and moderately effective against yellow stem borer and comparable to the 

insecticide monocrotophos @ 500 ml of formulation/ha. 

Under All-India Coordinated Rice Improvement Programme (AICRIP) of DRR, three commercially available 

B.t. formulations viz. Delfin 85%, Dipel 3.5% and BTKII have been evaluated @ 1500 g and 2000g of the 

product per hectare; for four seasons i.e. kharif 1995, 1996 and rabi 1996 and 1997 (DRR 1995, 1996, 

1997). These have been mainly aimed against leaf folder complex and to see if at all they are moderately 

effective against stem borer or not. The results revealed that all the three formulations were almost 

similar in moderately lowering leaf folder damage over locations, but the effectiveness against stem borer 

was marginal (Table 22). The Bt formulations were, in general, registered better effectiveness at higher 

dose than at lower dose. However, these were inferior to check insecticide chlorpyriphos @ 500 g a.i. /ha. 

Synergism of biopesticides with chemicals 

Rao et. al. (2003) in the field experiments at New Delhi noticed that the Bt formulation Biobit DF @ 750 

g a.i. /ha alone recorded moderate reduction in leaf folder damage but harboured highest predator 

populations. In combination with the insecticides like flufenoxuron (100 g a.i./ha) profenophos (750 g 

a.i./ha). Biobit exhibited excellent control of leaf folder and also conserved natural enemies. Gu et al., 

(1993) from Shanghai Academy of Agricultural Sciences, China observed a synergistic activity of aqueous 

concentrate of Bt with 25% dimethypo (thiosulfuric acids, S-[-2-(dimethylamino)-1,3-propanediyl] ester 

sodium salt], against leaf folder, Cnaphalocrocis medinalis under laboratory conditions with a toxicity 

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coefficient of 265 to 298 at 3:1 and 1:1 ratios. Exploiting this kind of synergism with non traditional 

chemicals will go a long way in commercial exploitation of B.t. formulations under practical field conditions. 

Feeding deterrency has been observed to be the major mode of effectiveness of Bt formulations like 

Dipel and Thuricide (Rombach et al., 1989). A method was standardised for testing this phenomenon by 

incorporating Bt formulations into the artificial diet of Asiatic rice borer, Chilo supressalis, allowing the 

larvae to feed on the diet and weighing both the larvae and artificial diet along with requisite standard 

controls. 

Nuclear polyhedrosis virus 

Mathai et al., (1986) from kerala, India made an attempt to exploit the synergism between nuclear 

polyhedrosis virus and traditional insecticides in the management of the rice swarming caterpillar, 

Spodoptera marutia and observed the virus in combination with the insecticides like quinalphos, fenthion, 

and permethrin exhibited better performance than the insecticides or the virus alone. 

Table 22 : Effect of Bt formulations on incidence of leaf folder and stem borer, rabi 1997 

Biopesticide 

Rate of 

formulation/ha 

LF (ADL/10 

hills (2) 

% DH (8) 

Stem borer 

% WE (4) 

Yield t / ha 

Delfin 85% 2000 23.2 8.7 7.6 4.9 

Delfin 85% 1500 25.3 9.8 8.2 4.6 

Dipel 3.5% 2000 25.3 9.6 7.6 4.8 

Dipel 3.5% 1500 29.5 8.8 8.0 4.5 

Biolep 2000 26.6 9.7 7.1 4.9 

Biolep 1500 26.4 11.3 8.0 4.6 

Chlorpyriphos 500 g a.i./ha 20.6 8.0 6.9 5.1 

Untreated control 57.5 12.2 10.7 3.9 

NB: The values in parenthesis indicate the number of observations on which the values in a column are 

based. 

(DRR, 1998) 

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MANAGEMENT OF GREEN LEAFHOPPER, VECTOR 

OF RICE TUNGRO DISEASE WITH INSECTICIDES 

In India, two species of green leafhoppers viz., Nephoteitix virescens and Nephottetix nigropictus act as 

vectors of the most important viral disease of rice namely rice tungro disease (RTD). The main host plant 

for Nephotettix virescens is rice, although, it can also survive on many grassy weed hosts. For Nephotettix 

nigropictus, the grass, Leersia hexandra is the main host and rice is only an alternate host although it can 

feed and multiply on rice. 

RTD is caused by two types of viral particles viz., rice tungro bacilliform virus (RTBV) and rice tungro 

spherical virus (RTSV) particles. The presence of both the particles in the host plant, rice causes the full 

expression of the symptoms of RTD. The presence of only RTSV cannot express any symptom, while the 

presence of only RTBV may produce mild symptoms. However, the presence of RTSV is very much essential 

for acquisition and transmission of the disease from one plant to another. 

TRANSMISSION OF THE RTD BY VECTOR 

The viral particles causing RTD are stylet-born in nature and are present only in the stylet of GLH. When 

a viruliferous insect starts feeding on the healthy host, the RTBV and RTSV are transmitted to the plant. 

The virus particles do not multiply in the body of the vector. Both the nymphs and adults of GLH are 

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GLH Adults RTD Infected field 

capable of transmitting RTD but in nymphs the virus particles are lost along with the exuvae at the time of 

moulting. Hence, the acquisition of the virus is essential after moulting for the vector to become viruliferous. 

In case of adults, the virus is transmitted until the inoculum gets exhausted in the stylet of GLH. The 

acquisition period i.e. the minimum period of feeding required for the vector to acquire the virus from 

diseased plant, in case of RTD, is approximately 6 hours. The transmission period i.e. the minimum time 

of feeding required for the viruliferous vector to transmit the viral particles into a healthy host is only 1- 

2 minutes in case of RTD. The viruliferous vector after acquiring the virus can transmit the disease upto 

about 3 days without further acquisition.


The transmission of RTD from weed hosts to rice appeared to be mainly by N. nigropictus while the 

transmission from one rice plant to another i.e. the spread of the infection after sowing and planting of 

rice crop appeared to be mainly by N. virescens. 

PLANT AGE IN RELATION TO SYMPTOM EXPRESSION 

Rice tungro disease (RTD) is systemic in nature in rice plant and also other weed hosts. It multiplies 

several fold immediately after inoculation. The period between the inoculation and expression of the 

symptoms is about 5 to 7 days. If the virus is transmitted to a young plant of 10-15 days old; then, within 

15 to 20 days the plants will become orange yellow and stunted with reduced tillering. Similar symptoms 

are observed if the infection occurs in 25-30 days seedlings (just before transplanting). These symptoms 

appear at the time of crop establishment in the main field and the crop may not mature properly and may 

not produce any grain. If the infection occurs at /after about 40 to 50 days after transplanting or in grown 

up crop, full expression may not be visible and the plants may turn orange yellow only towards harvest. 

Thus, the extent of losses caused by RTD in rice depends mainly on the age of the rice plant at the time 

of inoculation of virus into the plant. 

Integrated management of RTD 

Among the components of IPM available for management of RTD, host-plant resistance to the vector, the 

virus and both is the chief component. Host-plant resistance to the vector has been exploited to some 

extent by traditional breeding approaches. However, it was not successful in containing the spread of 

RTD. Hence, molecular approaches / immunological approaches to contain the multiplication of the virus 

in the host-plant have been attempted but with limited success. 

Cultural management of the vector by keeping the bunds free from weeds acting as alternate hosts to 

both the vector and the viruses appear to be a logical strategy. Synchronous planting of the crop in 

endemic areas can also contain the disease spread. Nitrogen management can also play some role in 

containing the losses caused by RTD. Like in the case of any other insect pest, nitrogen application can 

enhance the multiplication of the vector and indirectly enhance the spread of RTD. But, there are claims 

that nitrogen application can mask the effect of RTD at symptom expression level thus, can help the 

affected crop to produce slightly higher yield. But the virologists do not accept this claim and continue to 

argue that excess nitrogen may temporarily mask the symptom expression, but, the yield enhancement 

will not be there because the excess N will finally get converted into excess viral coat protein. 

Utilization of insecticides for management of the vector 

During late 1960’s and 1970’s when RTD was rampant in many rice growing tracts in India and also in 

many other countries in the world, it was thought that management of the vector with the help of insecticides 

can lead to successful management of RTD. Based on the available technology at that time, granular 

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insecticides like phorate and carbofuran were recommended for application in the nursery as well as in 

the main field. The dosages are in the range of 1000 to 1500 g a.i. /ha. The application was done in 

standing water and the water was inundated for three to four days to enhance the uptake of the active 

principles of the insecticides into the rice plant, thereby, GLH feeding on the foliage is controlled effectively. 

In many of the cases, this was helpful for containing the multiplication of GLH but not the virus transmitting 

ability of the virulent insects living in rice fields. 

ORGANOPHOSPHATES AND CARBAMATES 

During late 70’s and 80’s sprays of organophosphates like monocrotophos, acephate and carbamates 

like carbaryl were extensively employed for the management of vector in RTD endemic areas. These 

insecticides also can contain the multiplication of the vector but cannot prevent the transmission ability 

from one plant to other. Moreover, the sprays in general are less persistent than granular insecticides. 

Hence, more frequent applications of these insecticides were necessary. All the above insecticides do not 

have the quick knockdown kill of the vector, which is very much essential for successful prevention of the 

transmission of RTD viruses into healthy plants. 

SYNTHETIC PYRETHROIDS 

During 90’s, a thorough search was made to observe the effectiveness of later groups of insecticides 

available during those periods. Synthetic pyrethroids possess good knockdown kill as well as excellent 

persistent toxicity against GLH. The notable among the synthetic pyrethroids were the deltamethrin, 

cypermethrin, fenvalerate, chlothianidin, beta-cyfluthrin and lambda-cyhalothrin. These can be applied at 

dosages as low as 10 to 25 g a.i./ha. This strategy was economical and effective in tungro epidemic 

situations where outbreaks can be contained in the localized pockets. But later studies revealed that 

synthetic pyrethroids invariably cause resurgence of BPH and WBPH. This acted as a great deterrent for 

recommendations of synthetic pyrethroids for routine management of the vector and RTD in endemic 

areas. Hence, there was search for other groups of insecticides, which can contain GLH but do not cause 

BPH resurgence. 

ETHOFENPROX DOES NOT CAUSE BPH RESURGENCE 

During late 1990’s and early years of 21 st century there were new groups of insecticides like ether 

derivatives, neonicotinoids and phenyl-pyrazoles. The evaluation of the ether derivative ethofenprox 

revealed that this insecticide is effective at 50 g a.i./ha against green leafhopper, the vector of RTD but at 

the same time almost equally effective against BPH and WBPH and does not cause the resurgence of 

plant hoppers. Hence, this became an ideal choice for rice entomologists and pathologists for 

recommendation against GLH and RTD for routine application in endemic areas. This insecticide has 

extreme mammalian safety and also safety to predators of leaf- and planthoppers like spiders and mirid 

bugs. 

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NEONICOTINOIDS AND COMBINATION PRODUCTS 


Simultaneously neonicotinoids like imidacloprid, thiamethoxam and clothianidin and phenyl pyrazoles like 

fipronil and ethiprole have been evaluated against GLH as well as BPH and WBPH. Neonicotinoids are 

effective against GLH at as low as 20 – 25 g a.i./ha. These possess quick knockdown effect against GLH 

and also excellent persistent toxicity. However, the knock-down effect of neonicotinoids is not as high as 

synthetic pyrethroids. Hence, a further refinement has been introduced into RTD management technologies 

with the help of insecticides by evaluating and recommending combination products involving synthetic 

pyrethroids and neonicotinoids. The tank mixing of synthetic pyrethroids and neonicotinoids before spraying 

at recommended dosages was also found to be successful for containing the RTD by controlling the vector 

and also managing BPH and WBPH problem in rice ecosystem. In addition, such combinations have an 

added advantage of exploiting the beneficial effects of synthetic pyrethroids like their extreme effectiveness 

against lepidopteran pests like leaf folder, case worm and to some extent stem borers. This strategy can 

also be successfully employed in endemic areas as well as in routine epidemic situations. 

ROLE OF BUPROFEZIN IN VECTOR MANAGEMENT 

In addition to the combinations involving neonicotinoids with synthetic pyrethroids, combination products 

containing synthetic pyrethroids and the insect growth regulator buprofezin are highly useful in managing 

the vector without BPH resurgence. Synthetic pyrethroids @ 10 g a.i./ha coupled with buprofezin @ 80- 

100 g a.i./ha either as a formulation or tank mixing before spraying is highly useful and desirable for RTD 

management through vector control. This does not cause BPH resurgence and is also useful to check 

lepidopteran pests like leaf folder. 

MECHANICAL REMOVAL OF RTD INFECTED PLANTS 

If there is RTD infection in young plants immediately after transplanting and the infected plants are few, 

then removal of the infected plants followed by burning can greatly minimize the available inoculum to the 

vector. This followed by application of effective insecticides will be an excellent strategy in containing the 

disease in endemic areas. 

CROP ROTATION AND INSECTICIDAL MANAGEMENT 

Apart from utilizing the insecticide strategy for management of RTD and the vector, the planning of 

insecticide applications in the aftermath of epidemics is very much essential. If rice crop is followed by 

another rice crop, then crop rotation with other crops like ground nut or other legume crops like black 

gram, green gram and red gram can be grown to break the disease cycle and vector multiplication. If the 

rice crop is followed by another rice crop then the next rice crop should be protected very heavily starting 

from the emergence of seedlings in the nursery up to about 50 days after transplanting. This is very 

107


much essential as introduction of the virus inoculum in the nursery can again cause the same epidemic 

situation. 

CONCLUSIONS 

l The basic strategy for management of RTD should be by implementing IPM i.e. crop rotation, utilization 

of varieties resistant to vector and RTD, clean cultivation by removing the grasses acting as alternate 

ghosts for virus and vector as well as mechanical removal of RTD infected plants and burning them. 

l In endemic locations, the above methods should be supplemented with the use of effective insecticides 

like ethofenprox or combination products containing neonicotinoids and synthetic pyrethroids or 

buprofezin and synthetic pyrethroids either ready to use formulations or tank mixing. 

l If there is outbreak of RTD in non-endemic areas, crop rotation with legumes and heavy protection in 

the succeeding rice crop should be adopted. 

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FUTURE STRATEGIES FOR INSECTICIDE 

USE IN RICE IPM 

v It is quite unfortunate that some of the international organizations like IRRI have discontinued their 

programs on insecticide evaluation in rice. This trend would prove disastrous in achieving sustainable 

rice production in the developing countries. 

v As new insecticides are developed from time to time by the pesticide industry, it is in the best interest 

of rice farmers and rice entomologists to continue to evaluate insecticides against major and sporadic 

insect pests to assess their spectrum of effectiveness against rice pests. Thus, the entire responsibility 

of insecticide evaluation in rice rests with national rice testing programs in all major rice growing 

countries including India. 

v New insecticides have to be evaluated in as many locations as possible to assess their entire spectrum 

of effectiveness against the whole range of insect pests infesting at all stages of crop growth and in 

all parts of rice plant. For the last ten to twelve years ICAR is insisting on the insecticide evaluation on 

payment basis as a part of resource generation strategy at the institute level. This in fact has inhibited 

many Indian companies to get their products evaluated in All-India Coordinated Rice Improvement 

Program, as the costs involved are very high compared to their limited resources. Hence, it is advisable 

to reduce the present rates of insecticide evaluation in AICRIP Entomology programs to levels that 

are affordable by majority of the companies. 

v In the past, several methods of insecticide evaluation like nursery treatment, seedling root dip, rootzone 

application etc have been attempted, and some of them were found to be technically superior 

over traditional broadcasting of granules in standing water or spray applications. In view of spread of 

insect pests like BPH and WBPH in new areas and the special ecological niche they occupy in the rice 

ecosystem i.e. basal portion of rice stems; new methods of insecticide evaluation like control droplet 

application (CDA) and applications of insecticide spread-oils of the most effective insecticides like 

buprofezin and application of insecticides along with irrigation water wherever possible must be explored 

as a part of insecticide evaluation program in rice. 

v Insecticide induced insect resurgence in rice has been well documented particularly in case of BPH, 

WBPH and leaf folder. This phenomenon may occur in case of other pests like yellow stem borer, gall 

midge, leafhoppers etc., as new molecules with restricted spectrum of activity will be developed in 

future. Therefore, a special program on assessing the insecticide-induced resurgence of new molecules 

with respect to all the major insect pests of rice should form a part of Rice Co-ordinated Entomology 

Programme. 

v A rich diversity of natural enemies has been reported to be present, as part of rice ecosystem. These 

natural enemies play an important role in pushing down the population levels of major pests under 

normal conditions. Hence, the insecticides that are recommended against major insect pests must be 

109


with as minimum toxicity as possible, to natural enemies of all the pests present in rice ecosystem. 

Therefore, facilities for evaluating the toxicity of all the recommended insecticides to natural enemies 

under controlled conditions must be developed at few selected AICRIP Centers and data should be 

generated. Simultaneously field observations on natural enemy-insect pest dynamics/prevalence should 

also be made to evaluate the safety of new insecticides to natural enemies of major insect pests. 

v Development of insecticide resistance in any insect pest control program is an unavoidable consequence. 

Therefore, assessment of insecticide resistance development should be a part of rice entomology 

program in future. This work can be undertaken at few selected centers, with each centre tackling the 

problem with respect to one or two major pests. It is painful to admit that there are no insecticide 

resistance studies with respect to three major insect pests like yellow stem borer, leaf folder and gall 

midge. Although the practical difficulties involved in generating suitable information on these pests is 

understandable, attempts should be made to overcome these difficulties and keep a watch on insecticide 

resistance development in these major insect pests. The very fact that many insecticides recommended 

against yellow stem borer are not showing high degree of effectiveness in the present day scenario 

compared to that 20 – 25 years back, when the insecticides were first introduced into the market is 

an indirect indication that slow process of insecticide resistance development is going on in case of 

yellow stem borer. 

v In areas where organic rice is grown, botanical pesticides and bio-pesticides should form an integral 

part of package of practices for rice cultivation. However, with regard to botanical pesticides the work 

done so far indicated that the neem products are moderately effective against leaf folder, leafhoppers 

and planthoppers. Hence, recommendation against these pests can be made with either neem 

formulations or indigenously made neem seed kernel extract (NSKE). However, the problems relating 

to standardization of commercial neem formulations still persists. Bioassay techniques for the most 

susceptible insect species can form an effectiveness assessment strategy instead of merely depending 

on azadirachtin concentration in the formulation. In many instances, oil based neem formulations with 

lower azadirachtin concentration have shown higher effectiveness per unit concentration of azadirachtin 

compared to the water based formulations with high azadirachtin content in the formulation. 

v Among the bio-pesticides, B.t formulations are the most effective and well documented against 

lepidopteran pests like leaf folder and stem borer in rice. Commercial formulations of B.t show 

moderate effectiveness compared with insecticides but these can be formulated as a part of organic 

rice culture. Exploratory attempts to find new strains of B.t are already underway and they should be 

encouraged. Development of trans-genics with new and effective B.t strains should also be continued. 

v Studies on compatibility of insecticides with fungicides should also be continued in view of new pestdisease 

complexes emerging in different rice growing areas. As the insecticides specific to different 

groups of pests and fungicides specific to different fungal diseases are emerging, the studies on 

compatibility of the latest recommended insecticide-fungicide combinations should be attempted both 

under greenhouse conditions as well as field conditions so that they can form the ready made 

recommendation strategies against insect pest and diseases situations. 

110


v Soil factors greatly influence the effectiveness of soil applied granular insecticides in rice ecosystem. 

Among the soil factors, soil p H , soil EC, organic carbon as well as other physico-chemical properties 

are important. Hence, relative effectiveness of selected granular insecticides in soil with extreme 

physico- chemical properties must be studied to ensure the effectiveness of granular insecticides 

under diverse edaphic situations in which rice is grown. In view of the emerging rice growing strategies 

like SRI, where soil moisture lies below saturation level, the adverse effects of soil properties on 

effectiveness of granular insecticides must be assessed before the granular insecticides are 

recommended. 

v During kharif season, rainfall frequently washes off the insecticide sprays applied to rice crop. Therefore, 

detailed information on extent of loss of insecticide efficacy due to rainfall must be generated. This 

gives indications regarding the minimum time interval required between spraying and rain fall for 

realizing full effectiveness of applied insecticide against the pest or pests. 

v In IPM it should be remembered that insecticide use should be the last option for any given pest 

situation. The cultural, biological and mechanical options must be explored first as short-term strategies, 

while varietal resistance must be the long-term strategy. However, the principle of least possible 

disturbance in rice ecosystem should be the most important guideline in insecticide use in rice IPM. 

111


112 

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146 

The authors are grateful to Dr. 

B.C.Viraktamath, 

The authors are grateful to Dr. 

B.C.Viraktamath, ACKNOWLEDGEMENTS 

Project Director, DRR for his 

encouragement, providing 

Project 

facilities 

Director, 

and 

DRR for 

for 

his 

his 

inspiring 

encouragement, providing facilities and for his 

The foreword. authors are The grateful authors to Dr. are B.C.Viraktamath, thankful to 

Dr. 

inspiring foreword. The authors are thankful to 

Project T. Ramesh Director, Babu, DRR for Professor his encouragement, and Head, providing Department facilities of 

Entomology, 

Dr. T. Ramesh Babu, Professor and Head, Department of 

and for his ANGRAU inspiring for his foreword. critical comments. The authors The authors are thankful gratefully to 

acknowledge 

Entomology, ANGRAU for his critical comments. The authors gratefully 

Dr. T. Ramesh the Babu, contributions Professor of and Rice Head, Entomologists Department under of the Entomology, All India 

Coordinated 

acknowledge the contributions of Rice Entomologists under the All India 

ANGRAU for Rice his Improvement critical comments. Programme The authors (AICRIP) gratefully for evaluating acknowledge different 

insecticides 

Coordinated Rice Improvement Programme (AICRIP) for evaluating different 

the contributions and generating of Rice valuable Entomologists information. under Mrs. the Aparna All India Das, Coordinated Personal 

Assistant 

insecticides and generating valuable information. Mrs. Aparna Das, Personal 

Rice Improvement Gr. III who Programme typed the manuscript (AICRIP) for deserves evaluating appreciation. different insecticides Special 

thanks 

Assistant 

are due 

Gr. 

to 

III 

Senior 

who typed 

Technical 

the manuscript 

officers Sri. 

deserves 

Y. Kondala 

appreciation. 

Rao, for his help 

Special 

and generating valuable information. Mrs. Aparna Das, Personal Assistant 

in 

thanks 

photographic 

are due 

work 

to Senior 

and Sri 

Technical 

A.S. Rama 

officers 

Prasadfor 

Sri. Y. 

for 

Kondala 

editing, 

Rao, 

page 

for 

setting 

his help 

Gr. III who typed the manuscript deserves appreciation. Special thanks 

and 

in photographic 

cover design. 

work 

Drs.T. 

and 

Lingaiah 

Sri A.S. Rama 

and V. 

Prasadfor 

Laksmi Narayanamma 

for editing, page 

who 

setting 

are due to Senior Technical officers Sri. Y. Kondala Rao, for his help in 

worked 

and cover 

as Senior 

design. 

Research 

Drs.T. Lingaiah 

Fellows in 

and 

various 

V. Laksmi 

schemes 

Narayanamma 

and helped 

who 

photographic work and Sri A.S. Rama Prasad for editing and page 

in 

worked 

the conduct 

as Senior 

of 

Research 

Insecticide 

Fellows 

evaluation 

in various 

experiments 

schemes and 

are 

helped 

setting. Drs.T. Lingaiah and V. Laksmi Narayanamma who worked 

thankfully 

in the conduct 

acknowledged. 

of Insecticide evaluation experiments are 

as Senior Research Fellows in various schemes and helped 

thankfully acknowledged. 

in the conduct of Insecticide evaluation experiments 

are thankfully acknowledged.


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148

priciples of insecticide use in rice ipm

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