Traverse City Record-Eagle

Archive: Thursday

October 11, 2012

Ash trees continue to hurt from beetle

LANSING — The threat from a metallic green beetle continues to spread throughout ash trees in the Great Lakes region.

Many ash already are dropping leaves or changing color earlier this year than usual — both mechanisms that trees use to cope with drought, said Deborah McCullough, a forest entomologist at Michigan State University.

"It's possible some insect populations could increase next summer as a result of this year's drought, but that is just really hard to predict," she said.

It doesn't seem like emerald ash borers will be leaving the region any time soon, experts say.

"Michigan has the worst infestation," said Robert Mangold, associate deputy chief for research and development at the Forest Service. It's so bad in fact, that this year the agency stopped surveying Michigan for the invasive beetle.

Every county in Michigan is now infected with the ash borer, Mangold said.

And McCullough said, "Conservatively, there's probably 80 million dead ash trees in the southern half of Michigan's Lower Peninsula alone. There's limited funding to do those kinds of surveys, so they're concentrating on the states that don't have significant outbreaks yet."

Western forests last year experienced a decline in deadly pests like the mountain pine beetle, which damaged 3 million fewer acres than in 2010, but the emerald ash borer continues to thrive in the East, according to the Forest Service.

"The ash borer is the most destructive insect that's ever invaded North America," said McCullough. "It kills urban trees, landscape trees, forest trees and is affecting every species of ash in North America."

As of 2011, the beetle had invaded all eight Great Lake states and Ontario, according to the report.

Mangold said pesticide injections can save individual trees, but it's not a realistic method to treat vast forests.

"It's beyond eradication in most areas, especially in the Great Lakes," he said. "We are working on biological controls and management techniques that tree farmers can use, but we are concerned about our ash resource.

"We're trying to manage the pests but it just continues to spread," Mangold said.

The ash borer spreads mostly by flying. But the Great Lakes are also particularly vulnerable because they often hide in wood packing material used to stabilize vessel cargo. Regulations are in place that require using pesticides to kill the invasive bugs, but they aren't foolproof, Mangold said. "There's so much trade coming in that sometimes things get through," he said.

The beetle can spread in moving firewood and by traveling long distances with trees purchased from local nurseries.

The good news is that while destructive insects like the ash borer dominate the Great Lakes region, others like the gypsy moth have rapidly decreased. The moth defoliated less than 5,000 acres in 2011, compared with 1.2 million acres the year before, according to the Forest Service study.

The significant decrease is likely a result of the successive wet springs of the past few years, Mangold said.

JENNIFER KALISH writes for Michigan State University's Capital News Service

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