Zheng-Yu Luo

The spotted lanternfly (SLF), Lycorma delicatula (Hemiptera: Fulgoridae), has invaded several countries and caused significant losses to agricultural economy, especially in grapes, apples and kiwifruit production. Currently, chemical control is the primary method for managing this pest. In this study, we tested the contact toxicity of bifenthrin and lime sulphur on SLF eggs, as well as the residual toxicity of natural pyrethrins, bifenthrin, and thiacloprid on SLF nymphs. The results showed that bifenthrin, applied at 100 times the label rate, had the highest lethal effect on SLF eggs, with an adjusted mortality rate of 71.8 ± 8.5%. The addition of a penetrant, Engulf, did not further enhance ovicidal efficacy. For nymphs, the residual effect of thiacloprid and bifenthrin at label rates demonstrated 100% mortality within 48 h in laboratory bioassays. Similar efficacies were observed in short-term field experiments. However, the efficacy of bifenthrin declined significantly over time, while thiacloprid provided a long-lasting control, with mortality rates of 72.8 ± 5.9% and 46.7 ± 7.2% at 7 and 14 days, respectively. Although the combination of pyrethrins and mineral oil exhibited limited efficacy, with a 0-day (test immediately after the sprayed branches have dried) mortality rate of 41.5 ± 12.5%, its favourable environmental safety profile makes it a viable option for organic control strategies. In conclusion, bifenthrin at 100 times the label rate was the most effective against SLF eggs, while thiacloprid at label rates provided the longest-lasting control against SLF nymphs.

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.

Aggressive interactions between males are common when victors gain increased mating success but can result in severe injury or death for the defeated. Anastatus japonicus (Hymenoptera: Eupelmidae) is a solitary egg parasitoid of hemipteran and lepidopteran species. Here, we investigated lethal interactions between A. japonicus males and analyzed aggression behavior scaled with the male condition, number of competitors, number of presented females, and female mating status. The intensity of A. japonicus male aggressiveness increased with the number of competitors and the number of presented females but was not affected by male relatedness. The intensity and frequency of A. japonicus male aggressive interactions were greater when males competed for virgin females compared to mated females. Larger A. japonicus males won more contests than smaller males and honey-fed males defeated starved ones, where defeated males suffered the loss of appendages and/or died. Fighting appeared to be the norm in all-male groupings, regardless of the presence of females. A number of biological and ecological factors are deducted that likely contribute to the evolution of male aggressive behavior in A. japonicus.