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Smokey Winged wasp recruited in fight against Emerald Ash Borers

The smoky-winged beetle bandit preys on emerald ash borer and similar beetles. A new program monitors this wasp to help determine in EAB is present in an area. (University of Minnesota Extension photo by Jeff Hahn)

The emerald ash borer has proved an elusive foe to conservationists. It hides in the tree tops and its larvae stow away under the bark of the ash tree, making early detection difficult.

Scientists have tried a host of methods — purple sticky boxes, yellow pan traps and bark stripping — in a desperate effort to stop the destruction of the invasive wood boring beetle that has killed tens of millions of ash trees in over 20 states.

While the beetle can hide from humans, it's not as good at hiding from natural predators, such as the smoky-winged beetle bandit, also known as Cerceris fumipennis.

The University of Minnesota Extension office is looking for volunteers to locate and monitor these harmless wasps that build their nests in sandy soil.

"Baseball fields are where these wasps like to nest," explained Amy Rager, an educator with the extension office. "Their nests are in the ground, usually near the edge by the grass."

The wasps are harmless to humans. They use their stingers to paralyze their prey in order to bring it back to the nest for their young.

Their nests look similar to ant hills, with a hole in the middle where the wasp emerges. The wasp itself is one-half to three-fourths of an inch long. It has dark, smoky brown wings and one yellow band on the second segment of its abdomen. The female has three large yellow spots on her face.

The technique is called biosurveillance, or using another species to find the pest species. By watching what the wasp brings back to its nest, scientists can be alerted to new infestations of the emerald ash borer, Rager said.

"If even one is found, it ramps it up to another level," Rager said. "There is a plan in place in Minnesota for how the emerald ash borer is handled."

If an EAB is found, workers from the Department of Agriculture or the Department of Natural Resources would come out and survey the surrounding ash trees, Rager said.

Vigilance is necessary, as a DNR map shows Dakota County is under quarantine with infestations sighted in Apple Valley and Hastings. To view the map, go to

Volunteering takes only a few hours over one week during the summer.

A volunteer must first register with the office. Then, he must either locate a new nest or volunteer to watch an established nest.

Volunteers would visit the nest mid-day, four to six sunny days during peak activity in July and early August, and net any wasps returning with prey.

Volunteers would then take the beetle, release the wasp and store the beetles in the freezer in labeled vials provided by the Extension office.

At the end of the season, volunteers would mail the collected beetles back to the University of Minnesota for identification in a prepaid mailing box.

Since the program began in 2014, the office has engaged 91 wasp watcher volunteers who have put in 639 hours to capture 344 buprestid beetles, the family of beetles which includes the EAB. The effort has uncovered 59 wasp nests.

Success at finding new infestations has been slow, however.

"For the first time this last year we actually did find a wasp bringing back an emerald ash borer in an area we knew to have an infestation," said Jeff Hahn, an entomologist with the Extension office. "It's encouraging. It's going in the right direction."

He said there has not yet been a sighting in an area unknown to be infested.

"Not finding it doesn't necessarily mean it's not there," he said.

To sign up, go to