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

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 (Hemiptera: Aphididae). Despite its comparatively narrow host range, releases of B. communis may still constitute a risk to native aphid species. To estimate the risk of exposure of non-target aphids to B. communis, we merged assessments of temporal co-occurrence with projections of spatial overlap between B. communis and three native aphid species, and in-field measurements of the incidence of ecological filters that may protect these aphids from parasitism. Temporal cooccurrence was assessed between A. glycines and native aphids (Aphis asclepiadis, Aphis oestlundi, and Aphis monardae) at four different locations in Minnesota, USA. The degree of temporal overlap depended greatly on location and aphid species, ranging between 0 and 100%. All of the native aphids were tended by multiple species of ants, with overall 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. The extent of geographic overlap between B. communis and native aphids based upon Climex modeling was 17-28% for A. monardae, 13-22% for A. oestlundi, 46-55% for A. asclepiadis and 12-24% for the A. asclepiadis species complex. The estimated overall probability of potential exposure of B. communis on native aphids was relatively low (P = 0.115) for A. oestlundi and high (P = 0.550) for A. asclepiades. Physical and antmediated refuges considerably lowered probability of population-level impact on A. monardae, and could lead to substantial reduction of exposure for the other native aphids. These findings are used to make broader statements regarding the ecological safety of current B. communis releases and their potential impact on native aphid species in North America.

Multifaceted determinants of host specificity in an aphid parasitoid

“…We determined that B. communis specialization may result from both physiological and behavioral constraints, but ecological factors such as spatial/temporal overlap and refuges from parasitism may act to narrow the actual host range in the field (Wyckhuys et al 2007b(Wyckhuys et al , 2009). The parasitoid's host range involves primarily certain Aphis species that are not protected by endosymbionts or host-plant associations.…”

A ‘Goldilocks’ hypothesis for dispersal of biological control agents

“…Recently, a classical biological program has been initiated against A. glycines in the north central United States, with several Asian hymenopteran parasitoid species collected or screened and one species (the braconid Binodoxys communis) released (Heimpel et al 2004Hoelmer and Kirk 2005;Wyckhuys et al , 2008Wyckhuys et al , 2009Desneux et al 2009a, b;Chacón and Heimpel 2010). The interplay between exotic natural enemy dispersal and biological control may be especially noteworthy in this system, given the heteroecious life cycle of A. glycines (Fig.…”

The Endosymbiont Arsenophonus Is Widespread in Soybean Aphid, Aphis glycines, but Does Not Provide Protection from Parasitoids or a Fungal Pathogen

“…For the latter goal, we assayed three species of parasitoid wasp and one species of fungal pathogen. The first parasitoid species assayed was Binodoxys communis , which currently is the only exotic parasitoid to have been intentionally released in the United States to control the soybean aphid as part of a classical biological control program [42]. The second wasp, Aphelinus certus , has been identified from parasitized North American soybean aphids, although estimates of parasitism rates are still forthcoming.…”