Wasps may squash ash borer

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Tweet The answer to Michigan's struggle with the emerald ash borer could be lurking in the basement of Giltner Hall.

Hundreds of parasitic wasps, no more than 2 millimeters in length, are being kept there.

And if a proposal introduced by the U.S. Department of Agriculture is approved, the wasps could be released in the areas of Ingham and Jackson counties, where they would seek and destroy the eggs and larvae of the emerald ash borer.

"This has the potential to decrease the damage of the emerald ash borer," said Leah Bauer, an adjunct associate professor of entomology at MSU and a research entomologist with the USDA Forest Service. "I have a lot of confidence this will be of great benefit."

The USDA and MSU are collaborating in the research. The emerald ash borer is an Asian beetle, which was discovered in Michigan in 2002, said Ken Rauscher, director of the Michigan Department of Agriculture's pesticide and plant management division. The beetle, in larva form, feeds on the inner bark of ash trees, which disrupts the flow of nutrients and water through the tree.

Since the beetle was discovered in Michigan, it has destroyed up to 25 million ash trees in the state, costing cities and municipalities an estimated $40 million annually to remove the dead, dry trees, Rauscher said.

"The emerald ash borer has been one of the most significant forest pests we've ever dealt with," Rauscher said, adding that he supports the release of the wasps. "There's been a very substantial impact on an annual basis to the Michigan economy."

The parasitic wasps, which are native to China, are attracted to the ash tree because of its smell, Bauer said. Once the wasps arrive at an ash tree, they lay eggs inside emerald ash borer eggs or larvae, which prevent them from hatching into emerald ash borers.

"These parasites are almost like predators," she said.

Introducing a new species to help deal with an existing invasive species is common practice, Bauer said.

"Biological control is very standard practice for handling invasive species," she said. "You go to the country where it is natural and find the natural enemies."

Because the wasps won't completely wipe out the emerald ash borer and will bring the pest down to nonthreatening numbers, the parasite will always have a host, Bauer said.

"The only risk of danger of anything like this is close relatives of emerald ash borers," she said. "The potential benefit far outweighs the risk."

The release of the wasps would benefit the state, said Hugh McDiarmid, spokesman for the Michigan Environmental Council.

"The risks of using these wasps outweighs the risk of letting the ash bore run its course," he said. "It's a better solution than pesticides."

But he has questions, too.

"The fear is there will be unintended consequences," he said.

Those consequences include the possibility that the wasps could unintentionally affect other insects or animals in the ecosystem, McDiarmid said.

Although the release of the wasps won't eradicate the emerald ash borer, it's a step in the right direction, Rauscher said.

"We recognize this isn't the silver bullet," he said. "But we hope they will be able to control it."

Brian McVicar can be reached at mcvicarb@msu.edu.

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