Studies on insecticide resistance in leafhopper, amrasca biguttula biguttula (ishida) in bt cotton
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Date
2013
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UAS Dharwad
Abstract
Studies on insecticide usage, insecticide resistance and diversity in leafhopper,
Amrasca biguttula biguttula (Ishida) across major cotton growing districts of Karnataka and
nitrogen induced susceptibility on leafhopper population were under taken at the Department
of Agricultural Entomology, College of Agriculture, Dharwad during 2011-2013.
The insecticide usage pattern varied greatly between and within the locations
indicating no definite insecticide usage pattern among the major cotton growing districts of
Karnataka. In all the major cotton growing districts of Karnataka except Mysore,
monocrotophos and imidacloprid formulations were the primary choices of insecticides for
management of sucking pests in Bt cotton.
Among the nine insecticides bioassayed, monocrotophos registered higher LC50 value
during both the years followed by imidacloprid, thiamethoxam, acephate and acetamiprid
while, the lower LC50 value was registered by fipronil followed by clothianidin. The
botanical, azadirachtin 1500 ppm recorded higher LC50 value as compared to other nine
insecticides. Leafhopper population of Raichur and Yadgir districts recorded higher LC50
values to almost all insecticides under study, while Mysore district’s leafhopper population
recorded lower LC50 values to all insecticides bioassayed.
Higher mixed function oxidase enzyme activity was noticed in the leafhopper
population of Raichur followed by Yadgir, while lower activity was noticed in Mysore
district population.
The six district’s leafhopper COI gene sequences were confirmed as A. biguttula
biguttula cytochrome oxidase subunit I (COI) gene. COI sequence analysis showed higher
similarity among the leafhopper population of major cotton growing districts of Karnataka.
The cotton leafhopper population of all the six districts was taxonomically identified as A.
biguttula biguttula.
The incidence of leafhopper and leaf nitrogen content increased with the increase in
the nitrogen dosages. The toxicity results indicated that there was no such striking difference
in LC50 values among leafhopper population as influenced by dosages of nitrogen.