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

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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.