The Effect of Agricultural Riparian Buffer Width on Generalist Natural Enemy Diversity

Abstract

University of Washington Abstract The Effect of Agricultural Riparian Buffer Width on Generalist Natural Enemy Diversity Matthew Chabot Maria Chair of the Supervisory Committee: Professor Sarah E. Reichard School of Environmental and Forest Sciences Wooded stream buffers support food production, from fish to farms. While wider buffers of conservation woodlands do improve salmon habitat (Beechie & Sibley 1997), they decrease arable cropland. Riparian buffers do, however, benefit agriculture through erosion control, wind protection and habitat for beneficial species. Some of these beneficial species are termed "natural enemies," as they are the traditional biological control, or predators, of herbivorous crop pests. Many beetles and spiders are prime examples of natural enemies because of their generalist feeding on several families of crop pests (Landis et al. 2000, Landis & Wratten 2002). There is growing support that greater natural enemy diversity correlates to a greater control of crop pests (Lehman & Tilman 2000, Gardiner et al. 2009) Using the Shannon-Wiener diversity index I measured the diversity as well as the abundance of generalist natural enemies moving between fields and riparian buffers at different spatial scales (5', 15', 35', and 180' wide buffers from the stream) during a corn growing season. The 180 foot buffer exhibited significantly greater natural enemy diversity during early corn growth suggesting that larger buffers can provide greater biological control when crops are most susceptible to pest outbreak.