Harold_1997_Pestic.Biochem.Physiol_58_23

Resistance to profenofos and activities of enzymes associated with metabolism of organophosphorus insecticides were measured in larvae of the tobacco budworm, Heliothis virescens(F.), that were field-collected from Louisiana during the 1995 cotton growing season. High frequencies of profenofos resistance were recorded in all field-collected strains and were strongly correlated with esterase activity and moderately correlated with glutathioneS-transferase activity toward 1-chloro-2,4-dinitrobenzene. Mean levels of acetylcholinesterase sensitivity to inhibition by chlorpyrifos oxon were lower in some field strains than that of an insecticide-susceptible strain; however, acetylcholinesterase sensitivity and resistance were poorly correlated in all field strains. Finally, there was no correlation between resistance and activities of P450-monooxygenase towardp-nitroanisole or glutathioneS-transferase toward 1,2-dichloro-4-nitrobenzene. These results suggest possible contributions of both metabolic and target site mechanisms toward profenofos resistance in this insect.