none Injection of the insect growth regulator (IGR) azadirachtin into Manduca sexta larvae that were parasitized by Cotesia congregata adversely affected subsequent endoparasite development when the compound was administered prior to the first larval ecdysis of the wasps. The observed effects of azadirachtin on development of C. congregata differ significantly from those induced by other IGRs in parasitized M. sexta , suggesting azadirachtin has a unique, though as yet undefined, mode of action. Life cycle and development; Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts Manduca sexta (Sphingidae); Hymenopteran parasites; Cotesia congregata; Azadirachtin effects on parasite development Cotesia congregata (Braconidae); Development; Azadirachtin effects; Lepidopteran hosts; Manduca sexta; Azadirachtin effects on parasite development