Effects of Nicotine on Growth, Development, and Survival of the Tobacco Budworm (Lepidoptera: Noctuidae) and the Parasitoid Campoletis sonorensis (Hymenoptera: Ichneumonidae)

Abstract

When nicotine, the major tobacco alkaloid, was incorporated into an artificial diet, it significantly reduced the 7-d larval and pupal weight and prolonged the pupation time of larval tobacco bud worms, Heliothis virescens (F.). Nicotine was 3.7 times more toxic to tobacco bud worm larvae parasitized by Campoletis sonorensis (Cameron) than to nonparasitized larvae based on the ratio of LC50 values. The difference in LC50 was significant. However, slopes of log dose probitlines were not significantly different, suggesting the same nicotine mode of action in both groups. Nicotine between 0.05 and 0.1% wt/fresh wt in the host diet prolonged parasitoid larval development and hence adult emergence time of the solitary endoparasitoid, C. sonorensis , but parasitoid larval development after egression was not affected. At higher concentrations of nicotine (0.1-0.3% wt/fresh wt), a high proportion of fully developed parasitoid larvae failed to egress from the host and those that egressed failed to form cocoons and eventually died. Nicotine did not affect the weight of the parasitized host or the weight of the adult parasitoid.