Department of Agricultural Biology, College of Agriculture & Life Sciences, Jeonbuk National University, Jeonju, Korea.
Crop Protection R&D Center, Farm Hannong (LG Affiliated Co.), Nonsan, Korea.
PLoS One. 2022 Sep 2;17(9):e0274086. doi: 10.1371/journal.pone.0274086. eCollection 2022.
Monochamus alternatus is a major forest pest that spreads pine wilt disease in pine trees as a vector of pine wilt nematodes. Chemical insecticides used as fumigants to control overwintering M. alternatus in forests are highly toxic to the environment, so we investigated entomopathogenic fungus Beauveria bassiana ERL836 as an eco-friendly and alternative material to control overwintering M. alternatus. In this work, we evaluated the insecticidal activity of B. bassiana ERL836 against M. alternatus adults, the possibility of fungal colonization on pine tree bark, and finally the control efficacy of fungal pre-treatment on pine tree logs against emerging M. alternatus adults in semi-field and field conditions. M. alternatus adults were killed on the pine tree logs pre-treated with the B. bassiana ERL836. White conidia were observed not only on the surface of the dead adults but also on the pine tree logs, suggesting that the adults were killed by the fungus on the pine. A formulated ERL836 powder treatment on larvae-infested pine logs showed high insecticidal activity against adults, similar to that with the fungal powder suspension treatment, but we demonstrated that using the fungal powder was simpler than using the suspension in field conditions. Even in the field condition, the fungal powder treatment showed high insecticidal activity against M. alternatus adults, which we attribute to its ability to maintain fungal activity for a long time in field conditions by covering the pine tree logs with a film during overwintering. We confirmed that the risk that fungus-infected M. alternatus adults would spread the fungus to other non-target forest insects was low. Thus, even a high-concentration treatment in a specific area is unlikely to transmit the fungus outside that area, so it can be safely used to control this pine wilt nematode vector in forest ecosystems.
松墨天牛是一种重要的森林害虫，它作为松材线虫的载体传播松材线虫病。化学杀虫剂作为熏蒸剂用于控制森林中越冬的松墨天牛，对环境有剧毒，因此我们研究了球孢白僵菌 ERL836 作为一种环保和替代材料来控制越冬的松墨天牛。在这项工作中，我们评估了球孢白僵菌 ERL836 对松墨天牛成虫的杀虫活性、真菌在松树树皮上定殖的可能性，最后评估了真菌预处理对原木中松墨天牛成虫的控制效果，在半田间和田间条件下。经球孢白僵菌 ERL836 预处理的松树原木上的松墨天牛成虫全部死亡。不仅在死亡成虫的表面，而且在松树原木上也观察到白色分生孢子，表明成虫是被真菌在松树上杀死的。用含 ERL836 的制剂处理受幼虫侵害的原木对成虫表现出很高的杀虫活性，与真菌粉悬液处理相似，但我们证明，在田间条件下，使用真菌粉比使用悬液更简单。即使在田间条件下，真菌粉处理对松墨天牛成虫也表现出很高的杀虫活性，这归因于其在冬季覆盖松树原木的薄膜的情况下，能够长时间保持真菌活性。我们证实，感染真菌的松墨天牛成虫将真菌传播给其他非目标森林昆虫的风险很低。因此，即使在特定区域进行高浓度处理，也不太可能将真菌传播到该区域之外，因此可以安全地用于控制森林生态系统中的这种松材线虫载体。
