Abstract: Induction of carboxylesterase (CarEs) by insecticides and plant allelochemicals and de velopmental changes of CarEs were investigated during 1992-1996 in cotton boilworms, Helicover pa armigera (Hubner). The specific activities of midgut CarEs increased slowly before 5th day and then rose rapidly in larvae. The specific activity started to reduce from 8th day larvae to prepupae and then rose again. E2, E4, E5, E.6, E7 and E9 activities in nine isoenzyme hands obtained by polyacrylamide gel electrophoresis were higher using β-naphthyl acetate than a-naphthyl acetate as substrate, whereas El, E3 and E8 activities were reversed. Parathion, malathion, fenthion, SV1,methomyl and deltamethrin at sublethal dosage made the total activities of CarEs reduce, but malathion induced the activities of E4 and E5 in six isoenzyme bands at 48h after treatment by malathion and depressed the activities of El, E2, E3 and E6. Plant allelochemicals, rutin, quercetin and 2-tridaconone, can significantly induced Care activities of larvae.

Key words: Helicoverpa armigera, carboxylesterase, insecticide, plant allelochemical