With the number of broad-spectrum pesticides available for use declining as the EPA enforces the Food Quality Protection Act, there is renewed emphasis on alternative methods of pest control. We have been conducting a series of field and laboratory experiments designed to test the compatibility of the use of increased vegetation diversity with the use of selective pesticides in controlling aphid pests in a crucifer agroecosystem. Preliminary results indicate that plots of broccoli surrounded by bare ground harbor more insect pests (aphids) than those surrounded by weedy margins; furthermore, pest densities respond to an interaction between pesticide spray levels and margin type. In an effort to elucidate mechanisms underlying these results, we report on some behavioral experiments we conducted in which the movement behavior of a common predator in our system (Coccinella septempunctata) was quantified and compared to a correlated random walk model. We discuss differences recorded in beetle movement between bare ground and weedy margin plots, both with and without pesticide spray disturbances. Furthermore, beetle movement was sensitive to the spatial scale of experimental plots, suggesting that successful biological control by ladybird beetles may be a function of habitat vegetation diversity and scale.
Index terms: Brassica, Coccinella septempunctata, Myzus persicae, Brevicoryne brassicae, correlated random walk, vegetation diversity
The ESA 2001 Annual Meeting - 2001: An Entomological Odyssey of ESA