Unlike A. certus, Aphelinus glycinis feeds only on soybean and cotton aphids and passed all the official hoops for approval. Heimpel introduced it on a limited basis in Minnesota last fall.

“We are going to release hundreds of thousands of them in Minnesota this summer in replicated field trials to see if we can significantly control soybean aphids,” says Keith Hopper, research entomologist, USDA Beneficial Insects Introduction Research Unit. If A. glycinis fails to be the soybean aphid killer, Hopper says another stingless wasp called Aphelinus rhamni is near approval, and still another, Aphelinus coreae, is waiting in the wings.

Heimpel is optimistic. “The volunteer A. certus and introduced stingless wasps could provide the one-two punch that we need to really help soybean growers. Farmers won’t need to change what they are doing as long as they follow the Integrated Pest Management (IPM) guideline of 250 aphids/plant as the threshold before spraying insecticides.”

Aphid App, a pilot smartphone application developed by University of Guelph Entomologist Rebecca Hallet, already factors aphid and natural enemy numbers into spraying decisions.

Spraying early and often could destroy any hope of natural control by killing the good insects along with the bad. “If you are trigger-happy, you kill the natural enemies, which could cause the aphids to surge again if the temperatures and field conditions are right,” says Tracey Baute, entomologist with the Ontario Ministry of Agriculture, where the predator wasps have successfully controlled soybean aphids.

USDA’s Hopper is confident that natural enemies will turn the tide in the battle against soybean aphids. “A successful narrow host parasitoid like we are studying will make soybean aphids an occasional problem here.”