Cultivar mixtures have been studied for decades as a means for pest suppression. The literature, however, shows a large variability in outcomes, suggesting that we are unable to create mixtures that consistently suppress insect pests and attract natural enemies. A key gap in our understanding of how cultivar mixtures influence pest control is that few studies have examined the plant traits or mechanisms by which cultivar diversity affects pests and their interactions with natural enemies. The diversity of plant chemistry in a cultivar mixture is one trait dimension that is likely influential for insect ecology because chemical traits alter how predators and herbivores forage and interact. To understand how plant chemical diversity influences herbivores and their interactions with predators, we fully crossed predator presence or absence with monocultures, bicultures, and tricultures of three chemotypes of tomato that differed in odor diversity (terpenes) or surface chemistry (acyl sugars) in a caged field experiment. We found that the direct effects of plant chemotype diversity on herbivore performance were strongest in bicultures and depended on herbivore sex, and these effects typically acted through growth rather than survival. The effects of chemotype diversity on top‐down pest suppression by natural enemies differed between classes of chemical diversity. Odor diversity (terpenes) interfered with the ability of predators to hunt effectively, whereas diversity in surface chemistry (acyl sugars) did not. Our results suggest that phytochemical diversity can contribute to pest suppression in agroecosystems, but that implementing it will require engineering cultivar mixtures using trait‐based approaches that account for the biology of the pests and natural enemies in the system.

中文翻译：

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化学多样性而非品种多样性可预测食草动物害虫的天敌控制

人们已经研究了品种混合物作为抑制害虫的一种手段。但是，文献显示结果的差异很大，这表明我们无法创建能够持续抑制虫害并吸引天敌的混合物。在我们对栽培品种混合物如何影响害虫控制的理解中，一个关键的差距是很少有研究检查植物特性或机制，品种多样性通过这些特性或机制影响病虫及其与天敌的相互作用。品种混合物中植物化学的多样性是一个性状维度，可能会对昆虫生态产生影响，因为化学性状改变了食肉动物和草食动物觅食和相互作用的方式。要了解植物化学多样性如何影响食草动物及其与捕食者的相互作用，在笼养田间试验中，我们将三种化学类型的番茄的单培养，双培养和三培养完全消除了捕食者的存在与否，这三种化学型的气味多样性（萜烯）或表面化学（酰基糖）有所不同。我们发现，植物化学型多样性对草食动物性能的直接影响在双培养中最强，并且取决于草食动物的性别，这些作用通常通过生长而不是生存起作用。化学类型多样性对天敌自上而下抑制害虫的影响在不同的化学多样性类别之间是不同的。气味的多样性（萜烯）会干扰捕食者有效捕食的能力，而表面化学的多样性（酰基糖）则不会。我们的结果表明，植物化学多样性可以促进农业生态系统中的有害生物抑制，