Parasitism of beet armyworm larvae was assessed in south Georgia cotton from 15 July to 16 September 1992, and the toxicity of several commonly-used insecticides to the parasitoid Cotesia marginiventris was tested. Parasitism of beet armyworm larvae was high, with nearly half (46.2%) of all collected larvae parasitized. Eight species of hymenopteran and two species of dipteran parasitoids were reared from beet armyworm larvae. The larval parasitoid cotesia marginiventris was the most commonly reared parasitoid, accounting for 76.8% of all parasitism. Meteorus autographae, also a larval parasitoid, was the second most abundant parasitoid, accounting for 15% of all parasitism; however, it was abundant only in one county. C. marginiventris was found to be highly susceptible to organophosphate and pyrethroid insecticides in its pupal and adult stage. In contrast, the carbamate thiodicarb and insect growth regulator diflubenzuron had no effect on survival of pupal C. marginiventris and were considerably less toxic to adult parasitoids than were the organophosphate or pyrethroid materials. It is concluded that this parasitoid can have a substantial impact on beet armyworm populations.