Classical biological control of the soybean aphid, Aphis glycines (Hemiptera:Aphididae), and the affect of initial aphid densities on Binodoxys communis (Hymenoptera:Braconidae) parasitism and establishment

Since its introduction in North America, insecticides have been the primary management tool for soybean aphids. Such outbreaks are frequent despite the impact of predators commonly found in North American soybean fields. The parasitoid wasp Binodoxys communis is very important in Chinese soybean fields for aphid control but it is missing from the natural enemy community in North America. Efforts to release this exotic parasitoid into North America have begun. Beginning in 2007, USDA has given permission for the release of the parasitoid wasp, B. communis in the United States. In the summer of 2008 and 2009, we released B. communis at four research farms in Iowa and monitored its distribution and establishment in soybean fields. At a sub-set of these farms, we conducted a field experiment to determine if the parasitoids establishment was effected by the initial density of aphids. In order to obtain differential aphid density treatment groups, caged soybean plants were infested with aphids at various dates. When mummies (aphids parasitized by B. communis) were added to caged soybean plants, the average number of mummies tended to be higher for plants with lower initial aphid densities. In contrast, when B. communis adults were free to disperse throughout the field, treatment groups with low aphid densities contained on average, fewer mummies than those with high aphid densities.