Department of Entomology, Iowa State University, 2310 Pammel Drive, 339 Science Hall II, Ames, Iowa, 50011, USA.
Ecol Appl. 2021 Jun;31(4):e02295. doi: 10.1002/eap.2295. Epub 2021 Feb 17.
Western corn rootworm, Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), is a major pest of maize in the United States and is an invasive pest in Europe. Maize is the only agricultural crop on which western corn rootworm larvae can survive and this insect requires two consecutive years of maize cultivation to complete its life cycle. Transgenic maize producing insecticidal proteins derived from the bacterium Bacillus thuringiensis (Bt) is often used to manage rootworm populations. The first Bt trait, Cry3Bb1, was introduced in 2003, but larval resistance to this toxin appeared in northeastern Iowa in 2009. Rootworm management occurs on a field-by-field basis, but adult rootworm may disperse among fields. It is known that growing consecutive years of Cry3Bb1 maize within a field can lead to resistance, but the relationship of the surrounding landscape to the development of resistance is unknown. Using geospatial tools and publicly available land-use data, we examined circular areas (buffers) surrounding fields that had previously experienced high levels of rootworm injury to Cry3Bb1 maize and rootworm resistance to Cry3Bb1 maize (problem fields). We calculated the proportion of area inside each buffer planted to maize continuously for 1-9 yr, and compared these values to those for randomly selected control points throughout the state. We also calculated the proportion of the state planted to maize for at least three consecutive years for 2003 through 2018, and its relationship with the annual value of maize. We found that areas surrounding problem fields had significantly more continuous maize compared to controls, with the most continuous maize within 1.6 km of problem fields. We also found that the cultivation of continuous maize in Iowa increased significantly between 2003 and 2018, and this was correlated with average annual price of maize. We hypothesize a scenario in which continuous cultivation of Cry3Bb1 maize in local landscapes, driven in part by the increased value of maize, facilitated selection for Cry3Bb1 resistance. These results suggest that land use in areas surrounding problem fields affect the rate of resistance evolution and approaches for resistance management can be enhanced by taking a landscape-level perspective.
西方玉米根萤叶甲，Diabrotica virgifera virgifera LeConte（鞘翅目：叶甲科），是美国玉米的主要害虫，也是欧洲的入侵性害虫。玉米是西方玉米根萤叶甲幼虫唯一能够生存的农作物，这种昆虫需要连续两年种植玉米才能完成其生命周期。生产源自苏云金芽孢杆菌（Bt）的杀虫蛋白的转基因玉米常用于管理根萤叶甲种群。第一个 Bt 特性 Cry3Bb1 于 2003 年引入，但 2009 年在爱荷华州东北部出现了对这种毒素的幼虫抗性。根萤叶甲的管理是在逐个地块的基础上进行的，但成虫根萤叶甲可能在田间之间扩散。众所周知，在一个地块连续种植多年的 Cry3Bb1 玉米会导致抗性，但周围景观与抗性发展的关系尚不清楚。利用地理空间工具和公开的土地利用数据，我们检查了先前经历高水平 Cry3Bb1 玉米根萤叶甲伤害和 Cry3Bb1 玉米根萤叶甲抗性的地块（问题地块）周围的圆形区域（缓冲区）。我们计算了每个缓冲区内部连续种植玉米 1-9 年的比例，并将这些值与全州范围内随机选择的对照点的值进行了比较。我们还计算了 2003 年至 2018 年期间至少连续三年种植玉米的州内面积比例，及其与玉米年平均价格的关系。我们发现，与对照相比，问题地块周围的区域种植的连续玉米明显更多，而在离问题地块 1.6 公里范围内种植的玉米最多。我们还发现，2003 年至 2018 年间，爱荷华州连续种植玉米的比例显著增加，这与玉米的平均年价格相关。我们假设了一种情景，即部分受玉米价格上涨驱动，在当地景观中连续种植 Cry3Bb1 玉米，促成了对 Cry3Bb1 抗性的选择。这些结果表明，问题地块周围地区的土地利用方式影响了抗性进化的速度，通过采用景观水平的视角，可以增强抗性管理的方法。
