Parasitism of the soybean aphid,Aphis glycinesbyBinodoxys communis: the role of aphid defensive behaviour and parasitoid reproductive performance

The Asian parasitoid,Binodoxys communis(Gahan) (Hymenoptera: Braconidae), is a candidate for release against the exotic soybean aphid,Aphis glycinesMatsumura (Hemiptera: Aphididae), in North America. In this study, we examined preferences byB. communisfor the different developmental stages ofA. glycinesand investigated consequences of these preferences for parasitoid fitness. We also determined to what extent aphid defensive behaviours mediate such preferences. We found thatB. communisreadily attacks and successfully develops in the differentA. glycinesdevelopmental stages.Binodoxys communisdevelopment time gradually increased with aphid developmental stage, and wasps took longest to develop in alates. An average (±SE) of 54.01±0.08% of parasitizedA. glycinesalatoid nymphs transformed into winged adult aphids prior to mummification. No-choice assays showed a higher proportion of successful attacks for immature apterousA. glycinesnymphs compared to adults and alatoid nymphs. Also, choice trials indicated avoidance and lower attack and oviposition of adults and alatoid nymphs. The different aphid stages exhibited a range of defensive behaviours, including body raising, kicking and body rotation. These defenses were employed most effectively by larger aphids. We discuss implications for the potential establishment, spread and biological control efficacy ofA. glycinesbyB. communisin the event that it is released in North America.