Department of Entomology, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA.
Department of Entomology, Purdue University, West Lafayette, IN, USA.
J Econ Entomol. 2023 Jun 13;116(3):823-834. doi: 10.1093/jee/toad082.
Nearly all maize seed sold in the United States includes a neonicotinoid seed treatment (NST), meant to protect seedlings against early-season insect pests. For key pests, including western corn rootworm (Diabrotica virgifera virgifera LeConte) (D.v.v), insecticidal proteins derived from Bacillus thuringiensis (Bt) are expressed in plant tissues as alternatives to soil-applied insecticides. Insect resistance management (IRM) plans use non-Bt "refuges" to encourage survival of Bt-susceptible D.v.v., which maintains susceptible alleles in the population. In non-cotton producing regions, IRM guidelines require a minimum 5% blended refuge for maize expressing more than 1 trait targeting D.v.v. Prior work has shown that 5% blends yield insufficient proportions of refuge beetles to contribute reliably to IRM. Whether NSTs interfere with survivorship of refuge beetles is unknown. Our objective was to determine whether NSTs affect proportions of refuge beetles, and secondarily, to determine whether NSTs provide agronomic advantages over Bt seed alone. To reveal host plant type (i.e., Bt or refuge), we used a stable isotope (15N) to mark refuge plants in plots with 5% seed blends. To assess refuge performance between treatments, we compared proportions of beetles from respective natal hosts. In all site-years, NSTs showed inconsistent effects on proportions of refuge beetles. Treatment comparisons showed inconsistent agronomic benefits of NSTs when combined with Bt traits. Our results demonstrate that NSTs have a negligible impact on refuge performance and reinforces the assertion that 5% blends are serving little benefit for IRM. Plant stand and yield were not improved by NSTs.
几乎在美国销售的所有玉米种子都包含一种新烟碱类种子处理剂（NST），旨在保护幼苗免受早期季节的虫害。对于包括西部玉米根虫（Diabrotica virgifera virgifera LeConte）（D.v.v）在内的关键害虫，可以在植物组织中表达来自苏云金芽孢杆菌（Bt）的杀虫蛋白，作为土壤施用药剂的替代品。昆虫抗性管理（IRM）计划使用非 Bt“避难所”来鼓励 Bt 敏感的 D.v.v 的生存，这可以维持种群中的敏感等位基因。在非棉花生产地区，IRM 指南要求表达针对 D.v.v 的超过 1 个性状的玉米至少有 5%的混合避难所。先前的工作表明，5%的混合物产生的避难所甲虫比例不足以可靠地为 IRM 做出贡献。NST 是否会干扰避难所甲虫的存活率尚不清楚。我们的目标是确定 NST 是否会影响避难所甲虫的比例，其次是确定 NST 是否比单独的 Bt 种子提供农业优势。为了揭示宿主植物类型（即 Bt 或避难所），我们使用稳定同位素（15N）标记避难所植物在 5%种子混合物的地块中。为了评估处理之间的避难所性能，我们比较了来自各自亲代宿主的甲虫比例。在所有地点和年份，NST 对避难所甲虫的比例都表现出不一致的影响。处理比较表明，当与 Bt 性状结合使用时，NST 的农业效益并不一致。我们的结果表明，NST 对避难所性能的影响可以忽略不计，这也印证了 5%的混合物对 IRM 几乎没有益处的说法。NST 并没有提高植物的成活率和产量。
