Abstract: Mechanisms of insecticide resistance were studied in a field-selected resistant population (HJ-R) of Helicoverpa arrnigera. The fifth instar larvae of HJ-R strain possessed higher activity of esterase, glutathion S-transferase, monooxygenase than that of susceptiblestrain (HD-S) . There was no significant difference between the two strains in sensitivity of acetylcholinesterase to insecticide. The central nervous system of HJ-R strain showed 2-3 time more insensitive to the action of fenvelerate. The metabolic detoxication was the main reason of resistance to organophosphorus and carbamate insecticides. The monooxygenase seems to be the most important mechanism of carbamate resistance in HJ-R population. The resistance to pyrethroids were caused by both target insensitivity and metabolic detoxication of monooxygenase and esterase.

Key words: Helicoverpa armigera, carboxylesterase, monooxygenase, glutathion S-trans- ferase, target insensitivity