Insecticides can cause secondary pest outbreaks that weaken the benefit of chemical pest control. These detrimental nontarget effects motivate the use of alternative pest management strategies such as host plant resistance and intercropping. However, when alternative pest management strategies effectively suppress primary pests, they also have the potential to promote secondary pest populations via competitive release. The potato leafhopper (Empoasca fabae) is a key pest of alfalfa, and leafhopper‐resistant cultivars are being widely adopted by growers in the Midwest and Northeast United States. We conducted a field experiment comparing leafhopper‐susceptible alfalfa, leafhopper‐resistant alfalfa, and leafhopper‐resistant alfalfa intercropped with orchardgrass. Leafhopper‐resistant alfalfa reduced potato leafhopper abundance and protected the crop from protein loss, but there was no benefit of intercropping leafhopper‐resistant alfalfa with orchardgrass. Importantly, the abundance of a secondary pest, the pea aphid (Acyrthosiphon pisum), was twice as high in the leafhopper‐resistant plant treatments compared to the leafhopper‐susceptible treatment. Field sampling and microcosm experiments confirmed that the increase in pea aphids was caused, at least in part, by release from competition with leafhoppers. These results suggest that, when host plant resistance against insects is employed, efforts to monitor and manage secondary pest populations are warranted.

中文翻译：

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寄主植物抗性促进次生害虫种群

杀虫剂可引起继发性虫害暴发，削弱了化学虫害控制的益处。这些有害的非目标效应促使人们采用其他有害生物管理策略，例如寄主植物抗性和间作。但是，当替代性有害生物管理战略有效地抑制主要有害生物时，它们也具有通过竞争释放促进次生有害生物种群的潜力。马铃薯叶蝉（Empoasca fabae）是苜蓿的主要害虫，耐叶蝉的品种已在美国中西部和东北部的种植者中广泛采用。我们进行了田间试验，比较了与果园间作的叶蝉敏感苜蓿，抗叶蝉苜蓿和抗叶蝉苜蓿。抗叶蝉苜蓿减少了马铃薯叶蝉的丰度并保护了作物免受蛋白质损失，但将抗叶蝉苜蓿与果园间作没有好处。重要的是，有大量的次生害虫豌豆蚜虫（Acyrthosiphon pisum），是抗叶蝉植物处理的两倍。田间采样和微观实验证实，豌豆蚜虫的增加至少部分是由于与叶蝉竞争释放所致。这些结果表明，当采用寄主植物对昆虫的抗性时，就必须努力监测和管理次生害虫种群。