PESTICIDES AFFECT IMMATURE STAGES OF DIADEGMA-INSULARE (HYMENOPTERA, ICHNEUMONIDAE) AND ITS HOST, THE DIAMONDBACK MOTH (LEPIDOPTERA, PLUTELLIDAE)

Effects of pesticides on immature stages of Diadegma insulare (Cresson) and its host, the diamondback moth, Plutella xylostella (L.), were studied in the laboratory. Diamondback moth larvae parasitized by D. insulare were significantly less sensitive to ingested pesticides than were nonparasitized larvae 48 h after treatment. However, they were equally sensitive to pesticides through contact. Bacillus thuringiensis var. kurstaki (Berliner) and azinphosmethyl were significantly more toxic to parasitized larvae than permethrin, methomyl, and chlorothalonil if ingested. D. insulare adults emerging from pupae that formed from larvae surviving pesticide treatments tended to have more females than those in the control group. Except for B. thuringiensis and chlorothalonil treatments, percentage adults emerging from pesticide-treated pupae was significantly lower for D. insulare than for diamondback moth in either direct-dip or spraying bioassays. Lower pesticide sensitivity in immature stages of D. insulare may be important for effective integrated diamondback moth management.