A determined soybean aphid natural predator from Asia is controlling soybean aphids in Canadian fields, and may expand its range into the northern tier of the Midwest. This Asian stingless wasp, Aphelinus certus, is smaller than the period at the end of this sentence and arrived in North America at the same time as soybean aphids or shortly after that.

Ontario scientists found aphids killed by A. certus in 80% of the soybean fields they sampled in 2007, three years after they noted its arrival there. A. certus quickly teamed up with lady beetles, minute pirate bugs and other natural soybean aphid enemies to protect Ontario soybeans.

But A. certus has moved South across the border into Pennsylvania in 2007 and later into all of Minnesota’s soybean-growing areas.

 “Seeing them two years in a row is a big deal because it indicates they can overwinter here,” says University of Minnesota Entomologist George Heimpel. “We haven’t found them parasitizing (killing) aphids at very high rates yet, but that’s to be expected at this point of their move into the state.”


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With support from the soybean checkoff, Heimpel’s worked for 10 years to introduce beneficial insects to destroy soybean aphids. Most beneficial insect introductions require several attempts, and a species he introduced in 2007 didn’t survive a Minnesota winter.

A. certus, which showed up by accident, attacked every aphid USDA scientists showed it. However, A. certus may eventually be found to have a negative ecological impact, he says.