Interaction Effects of Farm-Scale Management of Natural Enemy Resources and the Surrounding Seminatural Habitat on Insect Biological Control

Abstract

The disruption of natural landscapes threatens the provision of ecosystem services, such as biological control. The surrounding non-crop habitat as well as local management practices may improve the biological control of crop pests. We studied the effect of adding flower strips on the control of aphids taking into account the effect of the surrounding landscape of 14 farms. We found significantly less aphids on farms with flower strips that had more surrounding non-crop habitats, which also had a greater proportion of mummies (parasitoids) early in the season under these same conditions. Predators, in contrast to parasitoids, responded more to the surrounding non-crop habitats later in the season, which coincided with their highest mean abundances. Our data suggests that aphid parasitism was enhanced by flowers, having a potential effect early in the season, which ultimately could explain the reduction in aphids thereafter. On the other hand, the effects perceived on general predator abundances seemed to be more related to their abundance and surrounding non-crop habitats. Flower strips of faba beans and buckwheat in the fields of farms with enough surrounding non-crop vegetation could therefore be an important management strategy to decrease brassica crop aphids in the field.