Toxicity of Eight Insecticides on Drosophila suzukii and Its Pupal Parasitoid Trichopria drosophilae

The pupal parasitoid <i>Trichopria drosophilae</i> (Hymenoptera: Diapriidae) has been evaluated as a biological agent of <i>Drosophila suzukii</i>. Integrated pest management strategies mostly rely on combined application of multiple insecticides and natural enemies. This study assessed the toxicity of eight common insecticides against <i>D. suzukii</i> in fruit orchards and the effects of semilethal and sublethal doses on <i>T. drosophilae</i>. The eight insecticides had higher toxicities to <i>D. suzukii</i> larvae with lower LC₅₀ values than those for adults. Adults and larvae showed high susceptibility to emamectin benzoate, spinetoram, lambda-cyhalothrin, abamectin, and sophocarpidine. The median lethal doses (LC₅₀) of lambda-cyhalothrin and imidacloprid to <i>T. drosophilae</i> adults were 60.41 mg/L and 100.58 mg/L, higher than the toxicities of the other six insecticides. Applying chlorantraniliprole, emamectin benzoate, sophocarpidine, abamectin, azadirachtin, and spinetoram resulted in low toxicity to <i>D. suzukii</i> pupae. However, the exposure of <i>D. suzukii</i> pupae or larvae to these insecticides at semilethal and sublethal doses decreased the parasitism or eclosion rate of <i>T. drosophilae</i>. These results improve our understanding of the effects of insecticide residues on <i>T. drosophilae</i> development and provide a basis for the combined use of chemical and biological options for managing <i>D. suzukii</i>.