LOCAL AND LANDSCAPE DRIVERS OF BIOLOGICAL PEST CONTROL IN AGRICULTURAL SYSTEMS
Perez Alvarez, Manuel Ricardo
Biological insect pest control by natural enemies is an important component of sustainable crop production. To capitalize on the potential benefits of biological control, however, we need a clear understanding of the factors underpinning the biological and ecological relationships between pests and their natural enemies in agricultural landscapes. In my doctoral research, I explored how local and landscape composition influence the abundance, behaviors, and traits of insect pests and natural enemies, as well as the complex ecological interactions between them. Chapter 1 shows how different insect pest species within the same cropping system have contrasting responses to landscape composition, with some species having positive relationships with the proportion of non-crop habitats, while other species show the opposite response. Such contrasting responses create the potential for counterbalancing effects for pest control, where strategies to reduce one species may increase the abundance of another. Chapter 2 demonstrates that the effectiveness of augmentative releases of predators to enhance pest control is affected by the composition of the surrounding landscape. I found that increasing enemy abundance through augmentation may have net positive effects on pest control, but only in complex landscapes where habitat heterogeneity can create favorable conditions for complementarity between augmented and resident enemies. Chapters 3 focuses on the critical role of predator body size as a predictor of pest suppression. We found that communities with even representation of small and large-bodied species have greater pest control than communities dominated by either small or large-bodied predators. By influencing the body size distribution of predator communities, landscape composition consequently mediates the magnitude of pest suppression. Chapter 4 shows that landscape composition not only affects the consumptive, but also non-consumptive effects of predators on prey. I demonstrated that pest populations from landscapes with higher predator abundance exhibited considerable reductions in plant feeding in response to the presence of predators alone. Importantly, such landscape-driven changes in predator abundance may lead to reduced plant feeding damage, even in the absence of actual predation. Overall, my research shows that agroecosystem management that aims to harness the benefits of biological control should consider a landscape perspective because processes governing pest suppression by natural enemies operate at scales greater than individual fields.
Brassica oleracea; Ecosystem services; Landscape composition; Pest control; Predation; Sustainable Agriculture
Poveda, Katja Andrea
Thaler, Jennifer S.; Nault, Brian A.
Ph. D., Entomology
Doctor of Philosophy
dissertation or thesis