Officials: Emerald ash borer reaches northern Minnesota

Emerald ash borers have been found in Duluth, marking the first discovery of the tree-killing pests in northern Minnesota, state agriculture officials said Friday.

Researchers found ash borer larvae in ash trees on Park Point in Duluth.

"This area has been a focus of ours for several years, ever since the discovery of (emerald ash borers) just across the border" in Superior, Wis., in 2013, Minnesota Department of Agriculture Entomologist Mark Abrahamson said in a statement.

"Now that we have found the insect," he said, "we can work with our partners in the city of Duluth and St. Louis County, and residents and businesses to take measures to slow its spread in the northern part of the state."

The department said Park Point would be put under quarantine to stop movement of ash trees and ash tree limbs off the land as well as all hardwood firewood as a way to stop the borers' spread.

Emerald ash borers kill ash trees by tunneling under the bark and feeding on the part of the tree that moves nutrients up and down the trunk, state officials said. Since it was discovered in Michigan nearly 20 years ago, the emerald ash borer has killed millions of ash trees across the Midwest and Canada.

In Minnesota, infestations have been found in the Twin Cities and in the state's southeast corner since the ash borer was first discovered here in 2009. With about 1 billion ash trees, the most of any state in the nation, Minnesota is highly susceptible to the pests' destruction.

Research suggests ash borer is only kept at bay when temperatures dive to 30 below zero. But officials say northern Minnesota's changing climate means the creatures are exposed less often to those extreme temperatures, giving them a window to grow in regions where they haven't been found before.

Because this is the first time that the ash borer has been identified in St. Louis County, the larvae specimens were sent to the United States Department of Agriculture for confirmation, which is expected within days, state officials said.

The biggest risk of spreading ash borer comes from people unknowingly moving firewood or other ash products harboring larvae, the agriculture department said.