Why did the Carabid Cross the Fence?

Physical barriers and biological control can be used to manage pests, but they have the potential to interfere with each other’s effectiveness. Exclusion fencing, which targets Delia radicum, could also create a barrier for poor-flying carabid beetles, polyphagous predators, from entering Brassica fields. I performed field and laboratory experiments to determine the permeability of exclusion fencing to the carabids Pterostichus melanarius and Bembidion lampros. The results show that the fence is permeable to both species, that as mesh size decreases, fence permeability decreases for B. lampros, and that B. lampros accumulates at the fence. A simulation model and cost-benefit analysis combined the results from the experiments with parameters from the literature to explore how carabids move across a field when a fence is present, and the fence’s cost to growers. Combining exclusion fence use with carabids and conservation biological control does not interfere with either tool’s effectiveness in controlling D. radicum.