By JENNIFER KALISH
Capital News Service
LANSING – The threat from a metallic green beetle is still spreading quickly throughout the ash of the Great Lakes region, despite a recent national report that said fewer trees died in 2011 from harmful insects in the United States than previous years.
The region’s drought can also seal the fate of sick and dying trees, the U.S. Forest Service reported.
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.”
While western forests last year experienced a decline in deadly pests like the mountain pine beetle, which damaged 3 million fewer acres than in 2010, 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 that 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. There are regulations that require using pesticides to kill the invasive bugs, but they aren’t foolproof, according to Mangold. “There’s so much trade coming in that sometimes things get through,” he said.
The beetle can spreads 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 been rapidly decreasing. 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.
The Forest Service also played a significant role, he said. “We have a big intensive program called Slow the Spread along that advancing front, and that has slowed gypsy moths.”
Jennifer Kalish writes for Great Lakes Echo.