The degree to which resident biota can inhibit the ability of an introduced biological control agent to establish and be effective is termed biotic interference. Studying biotic interference prior to a release using the actual agent is logistically difficult, however, due to quarantine restrictions. An alternative solution is to study biotic interference against a surrogate species in the intended range of introduction, with the expectation that biotic interference against the actual agent will be similar. This study assessed how biotic interference, mostly by generalist predators, may affect establishment of classical biological control agents of the soybean aphid, Aphis glycines Matsumura, in North America. The parasitoid Aphidius colemani Viereck was used as a surrogate for Asian aphidiine braconids such as Binodoxys communis (Gahan). We conducted a factorial field experiment that measured the effect of releasing A. colemani and of excluding resident natural enemies using field cages on soybean aphid populations. We also conducted molecular gut-contents analyses on predators collected in release plots to determine which species fed upon A. colemani. Releasing A. colemani in open field plots increased soybean aphid control beyond that observed in open field plots alone, despite indications that intraguild predation of A. colemani occurred. Thus, biotic interference was not sufficient to eliminate the contribution of A. colemani on soybean aphid suppression during the course of our experiment. Molecular gut-contents analysis revealed that at least two predators, Harmonia axyridis (Pallas) and Chrysoperla carnea Stephens, engaged in intraguild predation against A. colemani. The prolonged effect of intraguild predation on parasitoid establishment remains to be determined.
Bibliographical noteFunding Information:
We thank Jestke de Boer and Bob Koch for helpful advice when designing this experiment, Zeynep Sezen for statitistical advice, and Daniel Barta for field assistance. Also, the comments of Jacques Brodeur, Jetske de Boer, Kris Wyckhuys, Christine Dieckhoff and two anonymous reviewers significantly improved the quality of this paper. This work is funded by USDA-NRI and USDA-RAMP awards to D.A.L. and G.E.H., by the United States Environmental Protection Agency (EPA) under the Science to Achieve Results (STAR) Graduate Fellowship Program to J.M.C., and by the University of Minnesota Agricultural Experiment Station. EPA has not officially endorsed this publication and the views expressed herein may not reflect the views of the EPA.
Copyright 2008 Elsevier B.V., All rights reserved.
- Aphis glycines
- Biological control
- Biotic interference
- Harmonia axyridis
- Intraguild predation
- Molecular gut-contents analysis
- Soybean aphid