Multi-scale herbivore regulation in agroecosystems: role of multiple predator assemblages and bottom-up controls

益虫提供重要的生态系统服务，控制昆虫食草动物（害虫），每年可节省数十亿美元。然而，人们对天敌用来控制害虫的许多基本机制了解甚少，尽管存在自然防治剂，但害虫数量经常达到爆发水平。草食动物种群受多个空间尺度因素的调控。在景观尺度上，自然栖息地和农田可能成为攻击农业害虫的益虫的来源。先前的研究表明，景观的几个特征会影响天敌控制害虫的有效性，包括自然植被的范围、农田的大小以及与其他有益昆虫生长的作物的距离。然而，害虫与农田天敌之间发生的相互作用类型也决定了害虫的抑制水平。相互作用可能包括：1)田间植物作为害虫食物来源的影响，以及2)不同天敌之间的相互作用，这可能导致更高（更有效）或更低（天敌之间的干扰）的害虫抑制。我计划在商业领域进行一系列实验，以测试1)在不同程度的益虫孳生的景观中，当地因素对害虫控制的影响程度，2)导致益虫抑制害虫水平较高的景观特征，以及3)最有效的天敌组合。从理论角度来看，这些实验将为昆虫食草动物在多尺度上的调控提供新的见解。从更实用的角度来看，本研究结果将使我们能够专注于在农业景观中有效抑制害虫的天敌群体，保护和增强天然害虫防治剂提供的生态系统服务，并减少目前通过常规做法管理害虫的农药负荷和相关环境成本。

Beneficial insects provide important ecosystem services controlling insect herbivores (pests) that result in savings of billions of dollars per year. However, many of the basic mechanisms that natural enemies use to control pests are poorly understood and pest populations frequently reach outbreak levels despite the presence of natural control agents. Herbivore populations are regulated by factors operating at multiple spatial scales. At the landscape scale, natural habitats and crop land may act as sources of beneficial insects that attack agricultural pests. Previous studies have shown that several features of the landscape influence the effectiveness of pest control by natural enemies, including extent of natural vegetation, agricultural field size, and the proximity of other crops that harbor beneficial insects. However, the type of interactions taking place between pests and natural enemies in an agricultural field also determines the level of pest suppression. Interactions may include: 1) effects of the plants in a field as a food sources for pests, and 2) interactions among different natural enemies, that could result in both higher (more efficient) or lower (interference among natural enemies) pest suppression. I plan to conduct a series of experiments in commercial fields to test 1) the extent to which local factors affect pest control in landscapes that harbor varying levels of beneficial insects, 2) the features in the landscape that result in higher levels of pest suppression by beneficial insects, and 3) the combinations of natural enemies most effective at suppressing pests. From a theoretical perspective, these experiments will provide new insights into the regulation of insect herbivores at multiple scales. From a more applied perspective, the results of this research will allow us to focus on groups of natural enemies that are effective at suppressing pests in agricultural landscapes, to conserve and enhance the ecosystem service provided by natural pest control agents, and to reduce the current pesticide load and associated environmental cost of managing insect pests through conventional practices.