Langley, S. A. 2007. The role of non-cropped vegetation in facilitating the response of parasitoids to soybean aphids (Aphis glycines). Thesis, Michigan State University, East Lansing, Michigan, USA.

Soybean aphid, Aphis glycines, has become an important agricultural pest in the Midwestern United States. Here I present a study that identifies the parasitoid natural enemy community of the soybean aphid and the role non-crop habitat near soybean plays in attracting parasitoids to attack the aphid. The parasitoid community consists of Lysiphlebus testaceipes (Cresson), Binodoxys kelloggensis Pike, Stary, & Brewer, Aphelinus albipodus (Hayat & Fatima), Aphelinus asychis (Walker), Aphidius colemani Viereck, Diaeretiella rapae (McIntosh), and Praon sp. Lysiphlebus testaceipes was found abundantly attacking soybean aphids in soybean fields rather than aphids in adjacent non-cropped habitat. However, B. kelloggensis apparently did not discriminate between habitats when foraging for hosts.

I measured plant diversity within three non-cropped habitat treatments and compared plant diversity with parasitoid recoveries. Lysiphlebus testaceipes responded positively to increasing plant diversity in treatments mowed twice per month; B. kelloggensis showed a similarly positive relationship with increasing plant diversity, but within treatments mowed once at the beginning of the study. The simple farm practice of mowing field borders is not sufficient to aid in parasitoid transition to use soybean aphid in soybean, but the role of non-cropped habitat to attract parasitoids to soybean aphid is clarified when plant diversity of the field border is added to the analysis.

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