Potentiation between pyrethroid and organophosphate insecticides in resistant field populations of cotton bollworm Helicoverpa armigera (Lepidoptera: Noctuidae) in Pakistan

The combined action of pyrethroids plus organophosphates was assessed on putatively resistant field populations of Helicoverpa armigera from Pakistan by using a leaf-dip bioassay. Ethion showed a good potentiation with bifenthrin, lambdacyhalothrin, cyfluthrin, betacyfluthrin, fenpropathrin, esfenvalerate, fluvalenate and tralomethrin. Profenofos was potentiating with bifenthrin but additive with lambdacyhalothrin. Methyl parathion also exhibited potentiation with bifenthrin. Contrarily, quinalphos produced an antagonism with bifenthrin. Chlorpyrifos potentiated lambdacyhalothrin in one population but had an additive effect in the other. A strong potentiation of pyrethroids by ethion in some populations indicates that esteratic detoxification is a key mechanism involved in imparting resistance to pyrethroids in Pakistani H. armigera.