Susceptibility Change of Helicoverpa armigera Hubner to Different Insecticides in Punjab

Relative toxicity of different insecticides was determined against third instar larvae of Helicoperva armigera (Hubner) oe cotton growing area of aunjab, usinu leaf disf residre technique of bioassay. The order of toxicity was deltamethrin>fenvalerate>chlorpyriphos> quinalphos>cypermethrin>carbaryl>alphamethrin>endosulfan. Based on the LC₅₀, values, the effective field dosages of these insecticides were computed. These dosages when compared with recommended dosages, suggested about 2 to 112-fold decrease in susceptibility of the pest population to different insecticides. The decrease in susceptibility of H. armigera to synthetic pyrethroids was she maximum. In the case of chlorpyriphos the computed effective dose and the recommended dose were found to be comparable.