SOME STUDIES ON THE TOXICITY OF CONVENTIONAL AND ...

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Pak. Entomol. Vol. 27, No.1, 2005
SOME STUDIES ON THE TOXICITY OF CONVENTIONAL AND NEW
CHEMISTRY INSECTICIDES AGAINST BRACON HEBETOR (SAY)
(HYMENOPTERA: BRACONIDAE) UNDER LABORATORY CONDITIONS
Rashad Rasool Khan, Muhammad Ashfaq and Shahnaz Akhtar Rana*
Department of Agri Entomology, University of Agriculture, Faisalabad.
Department of Zoology and Fisheries, University of Agriculture, Faisalabad.
ABSTRACT
Toxicity of two conventional (chlorpyrifos, Lorsban 40EC; profenofos, Curacron 50EC) and three new chemistry
insecticides (lufenuron, Match 5EC; emamectin benzoate Proclaim 1.9EC; and methoxyfenozide, Runner 25 SC), at
three doses i.e, recommended for field use against Spodoptera litura and 10% above and below the recommended dose
was determined against the adults of Bracon hebetor (Say) under laboratory conditions. Bracon hebetor (Say) was reared
on Galleria mellonella L. One day old freshly emerged adults of B. hebetor were used for bioassay in the vial method.
Chlorpyrifos proved to be toxic, yielding 100% mortality at 24 hours on 10% above the recommended dose. Profenofos
exhibited 100% mortality after 36 hours at higher dose rate. Emamectin benzoate showed least mortality i.e, 21.75, 25.25
and 28.25, at all the selected doses after 48 hours of exposure.
INTRODUCTION
The selective insecticides, less toxic to natural enemies
than to target pests, are helpful in integration of
biological control and chemical applications (Hull and
Bear, 1985). Bracon hebetor (say.) is an important ectoparasitoid
of various Lepidopterans larvae (Magro and
Parra, 2001). Bracon hebetor (Say) can easily be mass
reared and it has released in the field for effective control
of Heliothis and Helicoverpa spp. as reported elsewhere
(Radhika and Chitra, 1996; Heimpal, 1997). Cotton in
Pakistan is sprayed heavily with insecticides of various
natures to control pest insects (Malik et. al. 1999). It is
necessary to know the extent to which these insecticides
can affect parasitoids and predators before putting any
biocontrol program into practice. The toxicity of
synthetic organophosphates, carbamates and pyrethroids
to B. hebetor has been reported in the laboratory
(Guddewar et. al., 1992). Fenvalerate, cypermethrin and
decamethrin (deltamethrin) caused 42.22, 58.33 and
73.88% mortality of B. hebetor, respectively, after 72 hrs.
Endosulfan was less toxic with 23.88% mortality than
any of the pyrethroids (Guddewar et. al., 1992). A field
strain of B. hebetor has exhibited more resistance to
deltamethrin, cyfluthrin and malathion as compared with
the laboratory strain (Baker et. al., 1995). Parthionmethyl
was the most toxic insecticide, followed by
quinalophos, while phosphamidon was the least toxic and
carbaryl, moncrotphos and endosulfan showed a
moderate toxicity (Mandal et. al., 1995). Botanics has
also shown toxicity to B. hebetor. An aqueous suspension
and an ethanolic extract of ‘neem’ seed kernels (NSK) at
0.3, 0.6, 1.2, 2.5, and 5.0% concentrations, were tested
for ovipositional deterrency, toxicity, sterility and insect
growth regulatory effects on Bracon hebetor by
Ragurman and Singh (1998). Neither NSK extracts
delivered in the food nor by contact, influenced the B.
hebetor oviposition (parasitization). They also did not
cause parasitoid sterility through feeding, but they
showed feeding deterrent effects for a limited period.
Parasitoid eggs and pupae were also unaffected by the
extracts tested. The parasitoid larvae, however, were
killed by feeding on the contaminated host larvae and
also through contact with the ‘neem’ extracts. Among the
new chemistry insecticides spinosad was toxic to B.
hebetor. Spinosad exhibited marginal to excellent
selectivity but was highly toxic to natural enemies
(Bracon mellitor) (Kovalankov 2002). The present
studies were conducted with an objective of finding
selective insecticides against B. hebetor when the later
can be used in integration with chemical control of
Spodoptera litura.
MATERIALS AND METHODS
This research work was carried out in the Eco-
Toxicology Laboratories, Department of Agri.
Entomology, University of Agriculture Faisalabad,
Pakistan.
A. Rearing of Bracon hebetor (Say):
Bracon hebetor was reared on Galleria mellonella
(Pyralidae: Lepidoptera). The glass vials with fertilized
females of Bracon hebetor and the 4 th instar larvae of
Galleria mellonella were placed in an incubator at
29+1 � C and 65+5% r.h. Each vial contained one male and
one female along with 2-3 host larvae of the 4 th instar. A
cotton plug soaked in 20% honey solution was put in the
vials for parasitoid’s feeding. The parasitized larvae of

Galleria mellonella were collected in a new vial and the
females of B. hebetor were given healthy larvae of G.
mellonella for further parasitization.
B. Rearing of greater wax moth Galleria mellonella:
Adults were kept in plastic jars (diameter, 5cm and depth
30cm) along with cotton soaked with 20-30% honey
solution to feed. Folded paper sheets were put in jars for
egg laying. The paper sheets with eggs were transferred
to the artificial diet (crushed wheat, bees wax, dates juice,
yeast, and glycerin). The jars were placed in a growth
chamber at 30 ±1°C and 65 ± 5 % r.h. until adult
emergence.
C. Bioassay:
For bioassay study, the residual vials method was used.
The commercial formulations of chlorpyrifos, profenofos,
lufenuron, emamectin benzoate and methoxyfenozide
were obtained from the local market. The concentrations
of different insecticides were prepared on the basis of
their recommended doses against Spodoptera litura and
ten percent above and below the recommended doses. A
sample containing 2 ml of each insecticides concentration
was put in the vials with the help of dropper. The vials
were rolled with hands, then air dried because acetone
dries rapidly in the air. 30 (one day old) adults of Bracon
hebetor that were freshly emerged were introduced in
vials with the help of aspirator. Each concentration was
replicated four times. The vials were covered with muslin
cloth to prevent escape of parasitoids. The vials were
placed in growth chamber running at temperature 30
±1°C and 65 ± 5 %R.H. The mortality of adult parasitoids
was noted at 12, 24, 36 and 48 hours intervals. The data,
thus noted, were analyzed statistically at 5% level of
probability using Duncan’s Multiple Range Test.
RESULTS
The mortality of newly emerged adults of Bracon
hebetor, observed 12, 24, 36 and 48 hours after treatment
with different insecticides at different dose rates is
presented in Table 1.
All insecticides gave significant mortality of Adult
parasitoids as compared to the untreated check (Acetone).
Chlorpyrifos and profenofos were found to be the most
toxic for the parasitoid at their different doses after 36
hours of exposure. Complete mortality of the adult
parasitoid was observed in Chlorpyrifos with all doses
after 36 hrs of exposure. Emamectin benzoate was found
to be the least toxic for all of its doses used in this
experiment even after 48 hours of exposure of the
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Pak. Entomol. Vol. 27, No.1, 2005
parasitoid. A total of 28.25 adult parasitoids was killed
after 48 hours of exposure with 110ml per acre dose rate.
However, with the recommended dose of emamectin
benzoate (100ml/Acre) 21.75 insects were killed.
Methoxyfenozide and lufenuron were found to be
moderately toxic with their recommended doses (100ml
and 50 ml per acre, respectively) after 24 and 36 hours of
exposure. However, their higher doses (110ml and 55ml,
respectively) gave complete mortality after 48 hours.
DISCUSSION
The results of the present study showed that chlorpyrifos
was highly toxic for B. hebetor at all of its doses. Same
results were obtained by Baker and his co-fallows in
1995. They compared the field strains of B. hebetor with
laboratory strains for their resistance against various
organophosphates and other insecticides. They found that
laboratory strains were more susceptible to the
insecticides belonging to organophosphate group.
Different doses of profenofos were also found to be toxic
for B. hebetor after 36 hours of exposure. These results
were also in confirmation with the results of Baker et al.
1995 and Mandal et al. 1995. Amongst new chemistry
insecticides, emamectin benzoate was found to be least
toxic at almost all of its doses. There was no published
work on this insecticide for its toxicity against B.
hebeotor. The insecticides lufenuron and methoxy
fenozide were found to be moderately toxic.
No closely compatible data so far published similar to the
present work was available, thus, based on present results
obtained it can be concluded that none of the insecticides
can be considered completely safe for B. hebetor as far as
application on cotton is involved. Nevertheless, release of
parasitoids would be considered appropriate after 48
hours of application of insecticides on crop in case of
organophates and other persistent insecticides. The new
chemistry insecticides like emamectin benzoate,
lufenuron and mehtoxyfenozide, being less toxic are
hence recommended for integration. The parasitoid
should be released at least after 24 hours of the
application of these insecticides.
ACKNOWLEDGEMENTS
The present work is a part of Ph.D research of the first
author. Sincere thanks and gratitude are expressed to
Dr. Sohail Ahmed, Associate Professor, Department of
Agri. Entomology, for his kind supervision and valuable
suggestions for this research.

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Pak. Entomol. Vol. 27, No.1, 2005
Table 1: Mortality of newly emerged Bracon hebetor (adults) observed after exposure to various doses of
insecticides.
Insecticides Doses Mortality Mortality Mortality Mortality
After 12 hrs. After 24 hrs. After 36 hrs. After 48 hrs.
Chlorpyrifos 900 ml 23.25 abc 25.25 abc 30.00 a ---
(Lorsban 40 EC) 1000 ml 25.75 ab 28.25 ab 30.00 a ---
1100 ml 28.25 a 30.00 a --- ---
Profenophos 450 ml 17.75 cdef 20.25 cde 25.75 abc 28.25 a
(Curacron 50 EC) 500 ml 20.00 bcde 22.25 bcd 27.75 ab 30.00 a
550 ml 21.25 abcd 24.25 abc 30.00 a ---
Lufenuron
45 ml 15.25 def 18.75 cde 21.75 bcd 26.00 ab
(Match 5 EC) 50 ml 18.25 bcdef 19.25 cde 24.75 abcd 28.25 a
55 ml 20.75 abcd 23.00 abcd 27.25 ab 30.00 a
Emamectin benzoate 90 ml 11.25 f 13.00 e 18.50 d 21.75 b
(Proclaim 1.9 EC) 100 ml 12.50 ef 16.50 de 22.25 bcd 25.25 ab
110 ml 15.00 def 18.25 cde 24.50 abcd 28.25 a
Methoxyfenozide 90 ml 14.25 def 16.75 de 19.75 cd 23.00 b
( Runner 24 SC) 100 ml 17.00 cdef 19.25 cde 23.25 abcd 25.75 ab
110 ml 21.00 abcd 24.00 abcd 26.50 ab 29.50 a
Control Acetone 0.00 g 0.00 f 0.00 e 0.00 c
REFERENCES
Baker, J.E., D.K. Weaver, J.E. Throne, and J.L. Zettler.
1995. Resistance to protectant insecticide in two
field strains of the stored products insect parasitoid
Bracon hebetor (Hymenoptera: Braconidae). J.
Econ. Entomol., 88: 3, 512-519.
Guddewar M. B., Shukla A. and Saini M. L. (1992).
Relative toxicity of synthetic pyrethroids to adult
Bracon hebetor (Say) (Braconidae; Hymenoptera).
Pl. Protect. Bull. Faradiabad, 44, 16-17
Heimpel G. E., Antolin M. F., Franqu R. A. and Strand
M. R. (1997). Reproductive isolation and genetic
variation between two ‘strains’ of Bracon hebetor
(Hymenoptera: Braconidae). Biol. Contr. 9, 149-156.
Hull, L. A. and E.H. Beers. 1985. Ecological Sensitivity
modifying chemical control practices to preserve
natural enemies. In M.A.Hay. and D.L. Herzong
(eds), Biological Control in Agricultural Ecosystem.
Acad. Press, Orlando, Fla. pp. 103-121.
Kovalankov V.G. (2002). A biomethod for condition of
arthropods resistances to insecticides. Zashita-i-
Karantin-Res-Tenni. 5, 18-19.
Magro, S. R. and J. R. P., Parra, 2002. Biology of
ectoparasitoid Bracon hebetor Say, 1857
(Hymenoptera: Braconidae) on seven Lepidoptera
species. Scientia Agricloa 2001; 58 (4): 693 – 698.
Malik, A. K., S. Mansoor, N. A. Saeed, S. Asad, Y.
Zafar, J. Stanley and P. Markham, 1999.
Development of CLCV resistance cotton varieties
through genetic engineering. Mongr. Directorate
Agric. Inform. Pb, Pakistan. p. 3.
Mandal, S.K. and A.K. Somchoudhury, 1994.
Bioefficacy of commercial formulation of
insecticides against Bracon hebetor (say). Indian-
Journal of Entomolog. 57(1): 50-54.
Press, J. W., B. R. Flaherty and R. T. Arbogast, 1978.
Interaction among Plodia interpunctella, Bracon
hebetor (Say) and Xylocoris flavipes. Environ.
Entomol. 3(1): 183-185.
Radhika, P. and K.C. Chitra, 1998. Correlation between
life expectancy and adult emergence in Bracon
hebetor (Say) as influenced by host level nutrition.
Indian J. Pl. Protect., 26(1): 68-71.
Raguraman, S. and R.P. Singh (1998). Behavioral and
physiological effects of Neem (Azadirachta indica )
seed kernel extract on larval parasitoid, Bracon
hebetor. J. Chem. Ecol., 24, 1241-1250.
Reinert, J. A. and E. W. King, 1971. Action of Bracon
hebetor (Say) as a parasite of Plodia interpunctella at
controlled densities. Ann. Entomol. Soci. America,
64(6):1335-1340.