Toxicity of insecticides to the egg parasitoids Telenomus podisi and Trissolcus teretis (Hymenoptera: Scelionidae)

Abstract

This work aims to evaluate the toxicity of insecticides used for stink bug control to the egg parasitoids Telenomus podisi and Trissolcus teretis. We tested ethiprole and sulfoxaflor + lambda-cyhalothrin in comparison with thiamethoxam + lambda-cyhalothrin and chlorpyrifos. Three independent bioassays were conducted in the laboratory and repeated for each parasitoid species, to evaluate the effect of insecticides on pupal and adult stages of the parasitoids and the effects of insecticide sprays on host eggs prior to parasitism. Ethiprole at concentrations of 100 and 133.3 g/100 L H2O was classified as harmless (class 1), according to the International Organization of Biological Control to both pupae and adults of T. podisi. When tested against T. teretis, ethiprole was classified as harmless (class 1) and slightly harmful (class 2), but it still was the most selective pesticide among the studied chemicals. When adult parasitoids of both species were exposed to sprayed host eggs, parasitism rates were similar. The other treatments triggered more severe negative side effects to the parasitoids, especially to adults. Overall, ethiprole was the least toxic compound among the studied products and should be preferred in integrated pest management aimed at preserving these biocontrol agents, while the other tested insecticides should be evaluated under semi-field and field conditions to verify their higher toxicity.