Identification of potential western bean cutworm (Striacosta albicosta) predators in field corn through molecular gut-content analysis

Western bean cutworm, Striacosta albicosta (Smith; Lepidoptera: Noctuidae), is a major pest of corn and dry beans in its historic and expanded ranges in the North American western Great Plains and Great Lakes Region, respectively. In corn, S. albicosta ear feeding damage can significantly reduce yield and introduce avenues for secondary fungal infections. Management practices currently rely on transgenic crops expressing effective Bacillus thuringiensis (Bt) protein, of which only the VIP3A protein is effective against S. albicosta, and/or labor-intensive scouting and chemical control. However, limited research on biological control options for this critical pest has been conducted. This study identifies key trophic interactions between S. albicosta and predatory arthropods in corn fields. Field surveys identified a community of 21 predator taxa present in Nebraska corn fields where S. albicosta eggs and larvae were present. The most common taxa were: Hippodamia convergens (Guérin-Méneville; Coleoptera: Coccinellidae), Coleomegilla maculata (De Geer; Coleoptera: Coccinellidae), Orius insidiosus (Say; Hemiptera: Anthocoridae), and green lacewings (Neuroptera: Chrysopidae). Additionally, molecular gut-content analysis via PCR confirmed the predation of S. albicosta by several well-known biological control agents, including H. convergens, O. insidiosus, C. maculata, Chrysopidae larvae and adults, and others. Coleomegilla maculata consumed more S. albicosta eggs and larvae than H. convergens in feeding trials, although egg consumption by C. maculata was unaffected by the presence of corn pollen, an important supplemental food for this species. Exploring the trophic interactions between S. albicosta and its predators will provide information necessary to improve conservation biological control for S. albicosta integrated pest management.西部豆夜蛾（Western bean cutworm, *Striacosta albicosta* (Smith; Lepidoptera: Noctuidae)）是其传统分布区北美西部大平原以及扩张分布区五大湖地区玉米与干豆的主要害虫。在玉米种植系统中，该虫蛀食果穗可造成显著的产量损失，并为次生真菌侵染提供可乘之机。当前的防治措施主要依赖表达有效苏云金芽孢杆菌（Bacillus thuringiensis, Bt）蛋白的转基因作物，其中仅VIP3A蛋白对西部豆夜蛾具有防效，同时辅以劳动密集型的田间测报与化学防治。然而，针对这一重要害虫的生物防治手段相关研究仍较为有限。本研究明确了西部豆夜蛾与玉米田内捕食性节肢动物之间的关键营养级互作关系。通过田间调查，在存在西部豆夜蛾卵和幼虫的内布拉斯加州玉米田中，共鉴定出21个捕食性类群群落。其中优势类群包括：多异瓢虫（Hippodamia convergens (Guérin-Méneville; Coleoptera: Coccinellidae)）、黄斑盘瓢虫（Coleomegilla maculata (De Geer; Coleoptera: Coccinellidae)）、小花蝽（Orius insidiosus (Say; Hemiptera: Anthocoridae)）以及草蛉（Neuroptera: Chrysopidae）。此外，通过聚合酶链式反应（Polymerase Chain Reaction, PCR）开展的分子肠道内容物分析证实，多种常见生防天敌均可捕食西部豆夜蛾，包括多异瓢虫、小花蝽、黄斑盘瓢虫、草蛉的幼虫与成虫等。取食试验结果显示，黄斑盘瓢虫对西部豆夜蛾卵和幼虫的取食量高于多异瓢虫，尽管玉米花粉作为该物种重要的补充营养源，其存在并未影响黄斑盘瓢虫的卵取食行为。阐明西部豆夜蛾与其捕食性天敌之间的营养级互作关系，可为优化针对该虫的保护型生物防治与综合害虫管理策略提供必要的理论依据。