Keweshan Ryan S, Head Graham P, Gassmann Aaron J
Department of Entomology, Iowa State University, Ames, IA 50011. Current Address: Department of Biology, Utah State University, Logan, UT 84321.
Monsanto Company, St. Louis, MO 63167.
J Econ Entomol. 2015 Apr;108(2):720-9. doi: 10.1093/jee/tov005. Epub 2015 Feb 27.
The western corn rootworm, Diabrotica virgifera virgifera LeConte, and the northern corn rootworm, Diabrotica barberi Smith & Lawrence (Coleoptera: Chrysomelidae), are major pests of corn (Zea mays L). Several transgenic corn events producing insecticidal toxins derived from the bacterium Bacillus thuringiensis (Bt) kill corn rootworm larvae and reduce injury to corn roots. However, planting of Bt corn imposes selection on rootworm populations to evolve Bt resistance. The refuge strategy and pyramiding of multiple Bt toxins can delay resistance to Bt crops. In this study, we assessed the impact of four treatments--1) non-Bt corn, 2) Cry3Bb1 corn, 3) corn pyramided with Cry3Bb1 and Cry34/35Ab1, and 4) pyramided corn with a blended refuge--on survival, time of adult emergence, and size of western and northern corn rootworm. All treatments with Bt corn led to significant reductions in the number of adults that emerged per plot. However, at one location, we identified Cry3Bb1-resistant western corn rootworm. In some cases Bt treatments reduced size of adults and delayed time of adult emergence, with effects most pronounced for pyramided corn. For both species, the number of adults that emerged from pyramided corn with a blended refuge was significantly lower than expected, based solely on emergence from pure stands of pyramided corn and non-Bt corn. The results of this study indicate that pyramided corn with a blended refuge substantially reduces survival of both western and northern corn rootworm, and as such, should be a useful tool within the context of a broader integrated pest management strategy.
西部玉米根萤叶甲（Diabrotica virgifera virgifera LeConte）和北部玉米根萤叶甲（Diabrotica barberi Smith & Lawrence，鞘翅目：叶甲科）是玉米（Zea mays L）的主要害虫。几种产生源自苏云金芽孢杆菌（Bt）杀虫毒素的转基因玉米事件可杀死玉米根萤叶甲幼虫，并减少对玉米根的损害。然而，种植Bt玉米会对根萤叶甲种群施加选择压力，促使其进化出对Bt的抗性。避难所策略和多种Bt毒素的叠加可以延缓对Bt作物的抗性。在本研究中，我们评估了四种处理方式——1）非Bt玉米，2）Cry3Bb1玉米，3）含有Cry3Bb1和Cry34/35Ab1的叠加玉米，以及4）带有混合避难所的叠加玉米——对西部和北部玉米根萤叶甲的存活、成虫羽化时间和大小的影响。所有Bt玉米处理方式均导致每个地块羽化的成虫数量显著减少。然而，在一个地点，我们发现了对Cry3Bb1具有抗性的西部玉米根萤叶甲。在某些情况下，Bt处理方式减小了成虫的大小并延迟了成虫羽化时间，对叠加玉米的影响最为明显。对于这两个物种而言，带有混合避难所的叠加玉米羽化出的成虫数量显著低于仅基于叠加玉米纯种植株和非Bt玉米羽化情况的预期数量。本研究结果表明，带有混合避难所的叠加玉米可大幅降低西部和北部玉米根萤叶甲的存活率，因此，在更广泛的害虫综合管理策略背景下应是一种有用的工具。
