Aphelinus certus Yasnosh (Hymenoptera: Aphelinidae) is an accidentally introduced parasitoid of the soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae) in North America and it has become one of the most common natural enemies of soybean aphids in its adventive range. It is unclear, however, if increased prevalence of A. certus has resulted in increased biological control. We conducted an exclusion-cage experiment designed to isolate the impact of parasitoids from that of other resident natural enemies (mainly predators) of the soybean aphid. We found that A. certus greatly outnumbered all other soybean aphid parasitoids, and that it significantly reduced soybean aphid populations over a time span of less than two weeks compared to controls. Moreover, parasitoids alone resulted in aphid densities that were statistically equivalent to the combined effect of predators and parasitoids. Across all treatment cages, there was a significant negative association between parasitism rate and aphid population growth, with predicted zero aphid growth occurring at a parasitism rate of 42.2%.
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We would like to thank David Andow, Emilie Snell-Rood, and Robert Venette for providing insightful comments on previous drafts of this manuscript. The undergraduate research assistants Taylor Pitel, Joey Sullivan, and Symone McClain helped enormously with field and laboratory work. Additionally, we would like to thank Keith Hopper for help with insect identification, Milan Plećaš for insights on data analysis, and Jacques Brodeur, Alexandre Leblanc and one anonymous reviewer for tremendously helpful comments during the review process. JMK was funded in part by the 2014-15 MnDRIVE Global Food Ventures Graduate Student Fellowship through the University of Minnesota, and a 2015-16 University of Minnesota Doctoral Dissertation Fellowship. Additional funding was provided by the Minnesota Soybean Research and Promotion Council (9-14N NCE) and the North Central Soybean Research Program (3TP620).
- Aphis glycines
- Biological control
- Glycine max
- Integrated pest management
- Parasitic wasps