Assessing the lethal effects of pesticide residue exposure on beneficial parasitoids and their host, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae)

Chemical control is currently the main strategy for managing brown marmorated stink bug, Halyomorpha halys (Stål). However, chemical pesticides can harm nontarget species, including natural enemies of H. halys. Pesticides with high toxicity to H. halys and low toxicity to its parasitoids need to be identified to support H. halys management. This is not only for natural biological control but also for preemptive classical biological control of H. halys by parasitoids. Here, we assessed the contact toxicity of residues of eight insecticides against H. halys and three of its main parasitoid species (Anastatus japonicus Ashmead (Hymenoptera: Eupelmidae), Trissolcus japonicus Ashmead (Hymenoptera: Scelionidae), Trissolcus cultratus Mayr (Hymenoptera: Scelionidae)). This study aims to provide valuable insights for preemptive classical biological control of H. halys using these parasitoids. Our results showed that A. japonicus exhibited higher tolerance to the tested pesticides, while T. japonicus was the most sensitive species. Among the pesticides, chlorantraniliprole had the lowest overall impact on all three parasitoid species. Additionally, acetamiprid, azadirachtin, and rotenone were found to be harmless to A. japonicus. Acetamiprid, however, was slightly harmful to T. cultratus. The remaining pesticides showed moderate to significant harmful effects on the parasitoids. For H. halys adults and fifth instars, the pesticides tested caused no mortality within the 24 h exposure. However, young nymphs were susceptible to the tested pesticides. Fenpropathrin had the highest toxicity to H. halys, killing 83.3%, 52.8%, and 19.4% of second, third, and fourth instars in a 24 h exposure. Fenpropathrin, acetamiprid, cyfluthrin, azadirachtin, and dinotefuran were all slightly harmful to the first instar nymphs. The other pesticides were harmless to H. halys in a 24 h exposure. Halyomorpha halys mortality increased with the contact time with the residue. Mortality of fourth and fifth instars of H. halys was >70% for fenpropathrin, cyfluthrin, dinotefuran, abamectin-aminomethyl, and acetamiprid if exposure continued for 7 d. Acetamiprid was effective in controlling H. halys nymphs but exhibited varying levels of toxicity towards the three tested parasitoid species, depending on the residue age and exposure time. Azadirachtin showed lower overall toxicity to beneficial insects, suggesting that these materials could be used to manage H. halys while minimizing harm to key beneficial species.