Intraspecific plant diversity can significantly impact insect herbivore populations in natural systems. Yet, its role as an insect pest control strategy in agriculture has received less attention, and little is known about which crop traits are important to herbivores in different landscape contexts. Moreover, empirical economic analyses on the cost‐effectiveness of varietal mixtures are lacking. We used varietal mixtures of Brassica oleracea crops on working farms to examine how two metrics of intraspecific crop diversity, varietal richness and number of plant colors (color richness), affect crop damage and the incidence and abundance of two insect pest species: Pieris rapae and Phyllotreta spp. We evaluated the context‐dependency of varietal mixtures by sampling early‐ and late‐season plantings of B. oleracea crops in farms across a gradient of landscape composition. We developed crop budgets and used a net present value analysis to assess the impact of varietal mixtures on input and labor costs, crop revenues, and profit. We found context‐dependent effects of varietal mixtures on both pests. In early‐season plantings, color richness did not affect Phyllotreta spp. populations. However, increasing varietal richness reduced Phyllotreta spp. incidence in simple landscapes dominated by cropland, but this trend was reversed in complex landscapes dominated by natural habitats. In late‐season plantings, color richness reduced the incidence and abundance of P. rapae larvae, but only in complex landscapes where their populations were highest. Varietal richness had the same effect on P. rapae larvae as color richness. Unexpectedly, we consistently found lower pest pressure and reduced crop damage in simple landscapes. Although varietal mixtures did not affect crop damage, increasing color richness corresponded with increased profits, due to increased revenue and a marginal reduction in labor and input costs. We demonstrate varietal mixtures can significantly impact pest populations, and this effect can be mediated by intraspecific variation in crop color. However, the strength and direction of these effects vary by season, landscape composition, and pest species. The association between varietal color richness and profitability indicates farmers could design mixtures to enhance economic returns. We recommend additional research on the benefits of intraspecific trait variation for farmers.

中文翻译：

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不同品种混合物对虫害的景观依赖性影响及其对农民利润的影响

种内植物多样性会严重影响自然系统中的昆虫食草动物种群。然而，其作为农业害虫控制策略的作用受到了较少的关注，而对于哪种作物性状对于不同景观环境中的食草动物很重要，人们所知甚少。此外，缺乏对各种混合物成本效益的经验经济学分析。我们在工作农场上使用甘蓝型作物的各种混合物，研究了种内作物多样性的两个指标，品种丰富度和植物色数（颜色丰富度）如何影响作物的危害以及两种害虫的发生率和丰度：菜青虫和毛竹spp。我们通过在梯度景观组成的农场中对油菜双歧杆菌作物的早季和后期种植进行采样，评估了品种混合物的背景相关性。我们制定了作物预算，并使用净现值分析来评估品种混合物对投入和人工成本，作物收入和利润的影响。我们发现各种混合害虫对两种害虫的背景相关影响。在早季播种中，色彩丰富度不会影响Phyllotreta spp。人口。但是，增加品种丰富度会减少毛竹spp。在以农田为主的简单景观中发生率较高，但是在以自然栖息地为主的复杂景观中这种趋势得到了扭转。在季末播种中，色彩丰富度降低了菜青虫幼虫的发生率和丰度，但仅在种群最多的复杂景观中才出现。品种丰富度对菜青虫的影响相同幼虫为色泽丰富。出乎意料的是，我们一贯发现在简单的景观中病虫害压力降低且农作物损害减少。尽管各种混合物不会影响农作物的危害，但由于收入增加，劳动力和投入成本的减少，色泽的增加与利润的增加相对应。我们证明品种混合物可以显着影响害虫种群，并且这种影响可以通过作物颜色的种内变异来介导。但是，这些影响的强度和方向因季节，景观组成和害虫种类而异。品种颜色丰富度和获利能力之间的联系表明，农民可以设计混合物以提高经济效益。我们建议对种内性状变异对农民的好处进行更多研究。