Effect of insecticide applications in soybeans on Trissolcus basalis (Hymenoptera: Scelionidae)

Field studies were conducted to determine the effect of the primary insecticides that are applied to control Louisiana soybean insect pests on the survival of an important biological control agent of stink bugs (Hemiptera: Pentatomidae). Adult egg parasitoids, Trissolcus basalis (Wollaston), were affected little by permethrin field applications, but methyl parathion had an adverse but short-lived effect on parasitoid survival. High levels of adult parasitoid mortality were observed only within the first 6 h following methyl parathion application. Neither insecticide affected emergence of parasitoids from their host eggs, suggesting that stink bug eggs provided a barrier to insecticide penetration. However, parasitoids apparently contacted insecticide residues when chewing through host egg shells to emerge, resulting in some mortality after emergence, caused by methyl parathion. The degree of this mortality was affected by three factors; parasitoid developmental stage at time of insecticide application, position of parasitized egg masses in the soybean canopy, and parasitoid gender. Overall, results of this study suggest a general compatibility between a major biological control agent of stink bugs. T. basalis, and insecticidal control of stink bugs and lepidopterous pests in Louisiana soybeans