Pattern of cross‐resistance in pyrethroid‐selected populations of Helicoverpa armigera Hübner (Lep., Noctuidae) from India

Abstract: In Helicoverpa armigera, withdrawal of selection pressure resulted in a two‐ to fourfold increase in susceptibility to synthetic pyrethroids and continuous selection enhanced the resistance level by four‐ to fivefold to the respective pyrethroids at the end of the 14th generation. Populations selected for resistance to one pyrethroid showed positive cross‐resistance to all other pyrethroids, but no cross‐resistance to endosulfan and thiodicarb. There was a significant increase in mixed‐function oxidase activity with advancing generation suggesting its possible role in the positive cross‐resistance among the pyrethroids. The induction of carboxyl esterases in pyrethroid‐selected populations may have resulted in the activation of indoxacarb, thereby accounting for the observed negative cross‐resistance.