Mother Nature's Pest-B-Gone

Tiny wasps could play a big role in minimizing the environmental impacts of pesticide use.

It wasn’t your typical summer job. While friends flipped burgers, babysat or worked on landscaping crews, George Heimpel spent his high school vacations rearing insects that eat other insects alive from the inside out.

The insects under his watch were parasitoid wasps, and the job, though exotic, was far from frivolous. Heimpel’s employer, a California company called Beneficial Biosystems, sold the rice-grain-sized, people-friendly wasps for natural fly control. Released into barnyards or stables, the wasps would lay eggs inside fly pupae. When they hatched, the larvae would feast on the innards of their hosts, providing a sort of self-perpetuating pest control that obviated the need for toxic chemicals.

“I liked working with insects, I liked doing something that had the possibility for helping the environment and I liked the people there,” Heimpel says. “It was fun.”

As summer jobs sometimes do, this one stuck. Today, as professor of entomology in the University of Minnesota’s College of Food, Agricultural and Natural Resource Sciences and Institute on the Environment resident fellow, Heimpel continues to spend much of his time working with parasitoid wasps in hopes of providing Earth-friendly ways to minimize insects’ adverse impacts on people.

Heimpel’s current area of focus is not fly-eaters, but wasps that attack tiny insects called aphids. Aphids are notorious competitors for human food supplies, cutting yields of crops by up to 50 percent in the case of bad infestations. The conventional way farmers reduce the toll is to spray infested fields with powerful pesticides, which not only kill their target but also have the potential to harm a variety of other species that get in their path, including honeybees, birds and fish.

In particular, Heimpel is homing in on control strategies for a relative newcomer to the North American pest scene: the Asian soybean aphid. Unheard of here before it showed up in a Wisconsin field in 2000, the aphid has spread so far that producers now spray tens of millions of acres of soybean fields—acres that previously needed no pesticides—each year.

Heimpel and colleagues have been testing Asian parasitoid enemies of the Asian soybean aphid in search of one that would, were it released into the environment, be able to keep the aphid in check without otherwise upsetting the ecosystem apple cart. The screening process is understandably rigorous, and the bar set high to prove no possibility of harming native species before receiving government permission to release the nonnative wasps.

“We’ve been doing tests to learn how other insects might be affected by the release of these Asian parasitoids,” Heimpel says. “The question is, do they pose a danger to native aphids?”

Five years into the project, the research team has gotten approval to release one parasitoid wasp species that has shown limited effectiveness in driving down soybean aphid populations. Several other species are undergoing safety testing in a quarantine laboratory.

Heimpel recently began exploring whether parasitoids might be good news when it comes to global warming as well. Working with Jason Hill, another IonE resident fellow who’s an assistant professor of bioproducts and biosystems engineering in CFANS, he’s comparing the carbon footprint of five different options for dealing with soybean aphids: three conventional pesticide treatments, a cropping strategy to reduce the aphid, and biological control using a parasitoid that serves as a natural control to soybean aphids in Asia.

In a separate study, Heimpel and IonE resident fellow David Tilman, a professor in the College of Biological Sciences, are co-investigators with agronomy and plant genetics faculty members Don Wyse and Craig Scheaffer on a $1 million U.S. Department of Agriculture grant led by agronomy and plant genetics associate professor member Gregg Johnson to assess whether growing biofuel plants might contribute to the biological control of soybean aphids. The researchers are evaluating the pest control benefits provided by insects that hang out in willow plantings adjacent to croplands, in prairie plantings adjacent to croplands and in settings in which both willow and prairie plants are planted near crops. 

“We’re going to look at the interface of those biofuel plantings and the surrounding productive agricultural land to see whether the biofuel plantings help with biological control,” Heimpel says.

Besides carrying out specific research projects, Heimpel is using his IonE resident fellowship to spread the word about the environmental benefits of parasitoid alternatives to conventional chemical pest control.

“Not that many people know about biological control,” he says, “so I can be an ambassador for that type of work.”

George Heimpel


PHOTO BY JOSH KOHANEK


Video: Eating Aphids from the Inside Out

Tiny wasps hold promise for helping control nonnative soybean aphids without pesticides. Watch how a similar wasp uses aphids as both nursery and buffet for its babies. Watch the video at video.nationalgeographic.com