The effect of undersowing cabbages with clover on the activity of carabid beetles

Intercropping has potential as an alternative to chemical methods of pest control, and one of its effects may be to provide a favourable environment for beneficial invertebrates, including polyphagous predators such as carabid beetles (Coleoptera: Carabidae). This paper compares pitfall catches of carabids from clover-undersown cabbages and cabbages which were kept weed free by hoeing. There were four undersowing treatments consisting of two clover seed rates combined with high and low sward heights. Two species of carabid, Pterostichus melanarius and Loricera pilicornis, were collected in higher numbers from the undersown plots, but four species, Bembidion tetracolum, Trechus quadristriatus, Notiophilus biguttatus and Amara apricara, were more frequent in the heed plots. All six of these species did not differ in numbers among undersown treatments. Two other species, Agonum muelleri and Bernbidion lampros, did differ numerically among undersowing treatments, but the biggest differences were early in the season; as the plant cover in the undersown plots increased, these species were also collected in higher numbers from the heed plots. It was concluded that carabid species differ in their responses to plant cover.