Habitat fidelity and risk of non-target impacts of the soybean aphid parasitoid Binodoxys communis

The extent to which marginally suitable hosts are accepted by a biological control agent has important implications for both pest suppression and environmental risks that the agent may pose. The soybean aphid parasitoid Binodoxys communis has a narrow host range and mainly attacks host species within the Aphidini. Our objective was to assess habitat fidelity and the extent of non-target impacts of B. communis under field conditions. We quantified parasitism of both target and non-target hosts on sentinel plants in a target (soybean) as well as a non-target (alfalfa) habitat. The target and non-target habitats were adjacent to each other and research plots were set up such that they were equidistant into both habitats. B. communis was mass-released centrally into 12x12 m plots that comprised a total of 4 transects perpendicular to the field edges and running into both the target and non-target habitat. Sentinel plants consisted of either soybean aphid-infested soybean plants or cowpea aphid-infested fava beans. These were set up in pairs of one soybean plant and one fava bean plant at 1.5 m intervals along each transect and left in the plots for a total of 36 hours per release. We determined the percentage of hosts parasitized at each distance from the field edges and also quantified the emergence rate of B. communis from each host species.