Impacts of cover crop diversification on attraction, dispersal, and pest suppression by two key generalist predators

Agronomic cropping systems are often highly disturbed, lacking alternative resources for natural enemies critical for suppressing pests. Under these conditions, natural enemy survival and biocontrol potential may be reduced.  As a conservation biological control approach, flowering cover crops may be introduced to provide nectar, pollen, and refuge habitat to improve the efficacy and survival of natural enemies. However, natural enemies may exhibit preferences toward specific flowering plants and different plant species may provide different resources. Therefore, multiple species insectary mixtures may be designed to support targeted natural enemies.  We established buckwheat, Fagopyrum esculentum, and cowpea, Vigna unguiculata, in monocultures and  mixtures adjacent to corn, Zea mays to test the effects of insectary cover crop diversification on the natural enemy community, predator dispersal between cover and cash crops, and potential for pest suppression. To measure these effects, we used sweep net sampling, protein-based mark-recapture and sentinel prey. Results suggest that predator abundance increases with increasing density of inflorescences and extrafloral nectaries. Coleomegilla maculata and Orius insidiosus, two key generalist predators, as well as crab spiders (Thomisidae) were more abundant in buckwheat monoculture  and buckwheat-cowpea mixture treatments than in the cowpea monoculture. Recovered protein-marked C. maculata and O. insidiosus indicated migration between the cover crop border and corn, as well as predation on sentinel prey. Despite higher predator abundance and confirmed predator dispersal, sentinel egg predation, while high, did not differ between treatments. Landscape factors may play a greater role than field-scale management in influencing predator dynamics at this site.