Landscape structure and biological control in agroecosystems

Biological pest control has primarily relied on local improvements in popul ations of natural enemies, but landscape structure may also be important. T his is shown here with experiments at different spatial scales using the ra pe pollen beetle (Meligethes aeneus), an important pest on oilseed rape (Br assica napus). The presence of old field margin strips along rape fields wa s associated with increased mortality of pollen beetles resulting from para sitism and adjacent, Large, old fallow habitats had an even greater effect. In structurally complex Landscapes, parasitism was higher and crop damage was lower than in simple Landscapes with a high percentage of agricultural use.