The hymenopteran parasitoids Cardiochiles nigriceps and Campoletis sonorensis are prevalent throughout the tobacco growing regions of the Southeastern United States. These two species of wasp are a valuable economic and biological tool in controlling tobacco budworm infestations in tobacco. The use of the systemic insecticide imidacloprid has become an industry standard in North Carolina tobacco production for its early season control and deterrence of sucking pests. The toxicological and sub-lethal effect of imidacloprid to Hymenopteran species is well represented in scientific literature. However, the potential for the developmental exposure of endoparasitoids has been largely ignored. This study examines how the rate of tobacco budworm infestations and parasitism are affected through the use of systemic imidacloprid. In field trials, parasitism rates were not significantly different. Higher infestation rates of tobacco budworm were observed in plots treated with imidacloprid. Greenhouse studies showed a difference between treatments with a higher rate of successful parasitism events in untreated plants. In topical LD₅₀ assays, imidacloprid had a greater toxicity to C. sonorensis compared to C. nigriceps. Possible explanations for these results, the toxicological effect of imidacloprid to the two parasitoid species, and plans for future experiments are discussed. (Reprinted with permission)