priciples of insecticide use in rice ipm

Insecticides in Rice IPM (DRR)
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
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