Do floral resources of bioenergy crops improve sugar status of natural enemies of soybean aphid?

The soybean aphid is the most important pest of soybean in North America. Currently, the primary method of controlling soybean aphid is pesticide application, although additional strategies are being explored and developed. Enhancing natural enemy populations is one of the strategies that could increase biological control and decrease pesticide use. Providing shelter habitats, either from agricultural practices or for overwintering, and providing additional food sources, such as alternative prey species or floral resources, can help natural enemies. Second-generation biofuel crops can potentially provide both of these and thus may support better biological control in addition to plant biomass production. Our aim was to determine whether perennial-based biofuel crops can improve the sugar status of natural enemies of soybean aphid by providing floral resources. We used three types of biofuel plantings within soybean fields: a polyculture herbaceous mix (high floral resources), willow monoculture (low floral resources) and alley cropping system of previous two. These treatments were compared with a soybean-only control. The sugar status of three groups of natural enemies (lady beetles, lacewings and hoverflies) is described as levels of gut sugar (fructose), blood sugars (sucrose and other sugars) and sugar reserves (glycogen). To determine the sugar status of natural enemies, we used cold and hot anthrone tests to distinguish between different types of sugars. We hypothesized that natural enemies captured in soybean fields with polyculture biofuel plantings and with alley cropping system would have higher sugar levels than natural enemies from fields with willow plantings or in control soybean fields.