Response of the soybean aphid parasitoid Binodoxys communis to olfactory cues from target and non-target host-plant complexes

The parasitoid Binodoxys communis (Gahan) (Hymenoptera: Braconidae) is a candidate for release against the Asian soybean aphid, Aphis glycines Matsumura (Homoptera: Aphididae), in North America. Using a series of Y-tube olfactometer assays, we recorded responses of naïve and experienced B. communis females to odors from both target and non-target host plant complexes. The non-target host plant complexes included three aphid species native to North America [Aphis monardae Oestlund, Aphis oestlundi Gillette, and Aphis asclepiadis (Fitch)] and one species presumed to be exotic to North America (Aphis nerii Boyer de Fonscolombe), all on their respective host plants. We also investigated whether the parasitoid distinguishes between volatiles from soybean infested with A. glycines vs. those of uninfested plants. Volatiles from A. glycines-infested soybean plants and several non-target host plant complexes elicited a response in B. communis, which seemed to be reinforced through oviposition experience. Wasps with experience on a specific host plant complex increased their response to odors of this complex. Neither naïve nor experienced wasps, however, preferred odors from target vs. non-target host plant complexes in choice tests. Our data also indicate that B. communis is unable to distinguish between volatiles from infested vs. uninfested soybean plants. This study shows that B. communis females respond to a broad array of olfactory stimuli, exhibit low fidelity for any particular odor, and employ some behavioral plasticity in their response to volatile cues. We discuss implications of these results for establishment of B. communis and potential undesirable non-target effects associated with the release of this species in North America.