Ash borers on their way to Minnesota

Emerald ash borer
The emerald ash borer is responsible for millions of dollars of damage to ash trees in Michigan, and it's spreading to other states. The adult borer is a metallic, coppery-green color and one-third to one-half inch long.
Photo by David Cappaert of Michigan State University, courtesy of

The emerald ash borer doesn't look like much of a threat. The winged, metallic-green beetle is only half-an-inch long. But ask Robin Usborne, who works with researchers at Michigan State University about the damage it can cause, and her answer is frightening.

"It could devastate and kill every single ash tree we have in North America if we don't try to get a handle on it," Usborne says.

The bug has already infested more than 40,000 square miles in North America. Usborne says the emerald ash borer is changing Michigan's landscape.

Emerald ash borer
State DNR officials say Minnesota has a lot at stake when the emerald ash borer shows up here. The state has the third largest population of ash trees in the nation.
Photo courtesy of Mn DNR

"If you drive along the major freeways into Detroit right now, you can start seeing the devastation as far as dead ash trees along the roads," Usborne explains. "You've got city streets that have been lined with ash that are now dead. You have folks taking out ash trees in communities and subdivisions that had huge ash trees. And they're just sick about it."

Researchers don't know much about the emerald ash borer. It was first discovered in the U.S. in Michigan in 2002, but scientists believe the bug arrived on cargo ships from China years earlier. The adult beetles nibble on leaves but don't cause much damage. It's the bugs' larvae that feed on the inner bark of ash trees, fatally disrupting the trees' ability to transport water and nutrients.

Left on their own, emerald ash borers spread at a rate of maybe a mile a year. But they can travel much faster when they get human help, for instance when people transport firewood. The U.S. Department of Agriculture has imposed a quarantine in states that already have the beetle. The quarantine prevents firewood, bark and wood chips from crossing state lines.

In Minnesota, several agencies are working to keep the emerald ash borer out of the state for as long as possible. Ash borers are capable of killing trees far more quickly than Dutch elm disease, according to Mike Schommer, with the state Department of Agriculture. Schommer says the public is key to fending off an invasion.

Damage from ash borer
Emerald ash borers create galleries under the bark of ash trees, and the damage can eventually kill the tree.
Photo courtesy of Michigan Department of Agriculture

"They really are a big, big part of this process in keeping this bug out, and the way they can do that is by not moving firewood, especially bringing firewood from one part of the state, or even from a different state, back home with them," he says. "If they're going camping in a different part of the state, buy the wood where you burn it. That's the message we're trying to get out."

The Minnesota House and Senate have passed legislation that would outlaw possession of firewood on state lands unless it's obtained locally from an authorized dealer. Lawmakers say the governor will likely sign the measure.

State DNR officials say Minnesota has a lot at stake. The state has the third largest population of ash trees in the nation. Ash is sometimes used to make things like baseball bats and axe handles. It's more often used as pulpwood in paper mills and wood products plants in northern Minnesota.

Val Cervenka, coordinator of the DNR's forest health program says if the emerald ash borer arrives in Minnesota, the economic impact could be in the billions. The bugs would likely destroy millions of ash trees in urban areas, and hundreds of million more trees in the forests.

"We have a huge ash component in our rural forested areas and it's going to affect tourism and the timber industry and these are two very big industries for Minnesota," Cervenka says. "So it would impact our state for many, many, many years."

Some researchers think an emerald ash borer invasion into Minnesota and other states is inevitable, unless they find a way to control the bugs. Scientists in Michigan believe one answer might be to introduce another foreign bug into the country; a tiny wasp, native to China, that feeds on emerald ash borers.

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