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 co-occurrence 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 ant-mediated 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.
Bibliographical noteFunding Information:
Acknowledgements This paper is dedicated to Robert J. O’Neil, a pioneer in the field of biological control and source of inspiration to many, who passed away in Feb. 2008. We would like to thank Norbert Brotz and Jeremy Chacon for help with field research. We are grateful to Susana Acheampong, Nicolas Desneux and Wang LiMin for providing unpublished data. This work benefited greatly from technical assistance by Robert Venette (US Forest Service). The help of David Voegtlin and James C. Trager in identifying the respective aphid and ant species was invaluable. We are also grateful to Bob Djupstrom, Ellen Fuge and the Minnesota DNR, Scientific and Natural Areas Program for their granting permission to conduct research in Minnesota prairie sites. Lastly, we would like to thank Jeffrey Corney and John Haarstad at the Cedar Creek Natural History Area for their assistance in selecting appropriate field sites. This work was funded in part by the multi-state USDA-RAMP project, in part by the North Central Soybean Research Council, and in part by the Minnesota Agricultural Experiment Station.
Copyright 2009 Elsevier B.V., All rights reserved.
- Biological control
- Community-assemblage studies
- Ecological risk assessment
- Prairie habitats
- Spatial modeling