Mortality of tobacco budworm larvae (Lepidoptera: Noctuidae) and emergence of Cotesia marginiventris (Hymenoptera: Braconidae) exposed to Bacillus thuringiensis and thiodicarb alone and in combination

Mortality of Heliothis virescens (F.) larvae and emergence of Cotesia marginiventris (Cresson) were evaluated on terminals collected from cotton in fields treated with Bacillus thuringiensis Berliner var, kurstaki and thiodicarb. Tests were conducted using B. thuringiensis and thiodicarb, independently and in combination. Insecticide rates were those recommended for resistance management in Arkansas. Results indicate that neither B. thuringiensis nor thiodicarb, alone or in combination, provided acceptable control of H. virescens larvae (<33%) by day 16. However, thiodicarb and thiodicarb/B. thuringiensis mixtures provided significantly greater control of H. virescens than did B. thuringiensis application alone. In addition, no significant advantage was gained with tank mixtures of B. thuringiensis and thiodicarb as compared to thiodicarb application alone. Parasitization increased early larval mortality (day 2) only in conjunction with the application of B. thuringiensis. Neither insecticide applied independently nor in combination had a significant impact on the emergence of C. marginiventris from H. virescens. Overall, while results indicated unsatisfactory control of H. virescens, findings indicated no detrimental effect on the larval parasitoid population at rates suggested for resistance management.