Entomology
William Snyder
Exploring the Relationship Between Predator Biodiversity and Biological Control
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As agricultural producers move away from the widespread use of broad-spectrum insecticides, the abundance and biodiversity of on-farm arthropod communities is increasing. Agroecologists have long suspected that greater natural enemy biodiversity will lead to more effective pest suppression, but little experimental work has explicitly examined this assumption. In two cropping systems, potatoes and collards, we have been manipulating species richness among the community of natural enemies attacking aphids, to measure the importance of predator species diversity for effective biocontrol. We have borrowed experimental designs from the “biodiversity-ecosystem functioning” literature that isolate the importance of species diversity per se from any confounding influence of predator abundance, species identity, or community composition. The photo above is of a large-scale field experiment where predator diversity was manipulated. Interestingly, in potatoes natural enemy biodiversity seems to have no consistent benefit for aphid control, while on collards biological control always improves when natural enemy communities include multiple species.
The differing importance of predator biodiversity on potatoes versus collards suggests that plants mediate predator biodiversity effects. I am interested in examining how differences in plant structure, and differences in herbivore community diversity, exert a bottom-up influence on predator diversity’s importance for pest control. Our predator biodiversity work thus far has included only arthropod predators, but we now know that insect pathogens in the soil are key natural enemies of many herbivores. We are beginning to examine the relative importance for herbivore control of below- versus above-ground natural enemy biodiversity.
Contact Information
William E. Snyder, Ph.D.
Associate Professor
Department of Entomology
Washington State University
PO Box 646382
Pullman, WA 99164-6382
Telephone: 509-335-3724
E-mail: wesnyder@wsu.edu
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