Impact of Binodoxys communis on soybean aphids (Aphis glycines) in an organic field

Soybean aphids continue to cause problems in the Midwest, and farmers need more economical and sustainable ways to manage these pests. Binodoxys communis is a specialist soybean aphid parasitoid recently approved for release in the U.S., although its ability to regulate pest densities in the field is still being evaluated. Factors that may impact its effectiveness include environmental conditions and initial release density. In this experiment we explored how initial release density of B. communis affected soybean aphid densities within an organic soybean field. There were four replications of three treatments: a control with no Binodoxys, 500 Binodoxys mummies, and 1000 Binodoxys mummies. Densities of aphids, emerged mummies, and non-emerged mummies were monitored and the latter reared out to assess parasitoid identity. Although Binodoxys were released successfully and there was evidence of reproduction in the field, successful recovery was extremely low (10.2% of identified adults). Several generalist parasitoid species were also recovered including Lysiphlebus testiceipes (47.7%), Aphidius (13.6%), and Aphelinidae spp. (21.6%). Even though it appears that Binodoxys populations did not persist at high levels throughout the season, aphid densities were reduced in plots where wasps were released, although the effect was transient. Because we could not document high densities of Binodoxys in the field, it may be that the results are not directly attributable to these parasitoids.