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Title: Potential exposure of a classical biological control agent of the soybean aphid, Aphis glycines, on non-target aphids in North America

item Kula, Robert

Submitted to: Biological Invasions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/5/2008
Publication Date: 6/22/2008
Citation: Wyckhuys, K.A., Koch, R.L., Kula, R.R., Heimpel, G.E. 2008. Potential exposure of a classical biological control agent of the soybean aphid, Aphis glycines, on non-target aphids in North America. Biological Invasions. 11:857-871.

Interpretive Summary: Parasitic wasps attack agricultural pests that cause billions of dollars of damage to crops annually. The wasps treated in this paper attack aphids, specifically exotic soybean aphid and native aphids on wild bergamont, evening primrose, and common milkweed. Increased knowledge of these wasps helps determine their positive impact as biological control agents, as well as the risk they pose to native aphids. This paper assesses the potential impact of an introduced wasp on three native aphids from sites in Minnesota, USA. The probability of potential impact of the introduced wasp on the native aphids was low except for one species on common milkweed. The species on milkweed is a suboptimal host, with most wasps failing to develop on this host in laboratory testing. This paper will be useful to scientists conducting research on control of soybean aphid, as well personnel at state and federal agencies involved in soybean aphid biological control.

Technical Abstract: In summer 2007, the Asian parasitoid Binodoxys communis (Hymenoptera: Braconidae) was released in North America for control of the exotic soybean aphid, Aphis glycines (Homoptera: Aphididae). Despite its comparatively narrow host range, releases of B. communis may still constitute a risk to native aphid species. To quantify this risk, we merged assessments of temporal co-occurrence with projections of spatial overlap between B. communis and 3 native aphid species, and in-field measurements of the incidence of ecological filters that may protect aphids from parasitism. Temporal occurrence was assessed between A. glycines and native aphids (Aphis asclepiadis, Aphis oestlundi, and Aphis monardae) at 4 different locations in Minnesota, USA. The degree of temporal overlap depended greatly on location and aphid species, ranging between 0% and 100%. Many native aphids were present before A. glycines appeared in soybean fields. All native aphids maintained strong community linkages, with levels of ant attendance ranging from 26.1% to 89.6%. During temporal overlap with A. glycines, 53 ± 11% of A. monardae colonies were partly found in flower heads of their host plant, with flowers acting as a physical refuge for this aphid. Extent of spatial overlap between B. communis and native aphids was 17-28% for A. monardae, 13-22% for A. oestlundi, 55-46% for A. asclepiadis and 12-24% for the A. asclepiadis species complex, depending on the modeled scenario. Cumulative probability of (potential) impact of B. communis on native aphids was low (P= 0.115) for A. oestlundi and high (P= 0.550) for A. asclepiades. Physical and ant-mediated refuges considerably lowered probability of population-level impact on A. monardae. Findings are used to make broader statements regarding the ecological safety of current B. communis releases and their eventual impact on native aphid species in North America.