Invaders: Emerald ash borer now in Duluth, zebra mussels still in Christmas Lake


Minnesota's fight to keep invasive species at bay saw a couple of setbacks Friday – one in the trees of Duluth, the other in the waters of a Twin Cities-area lake.

Different state agencies announced that emerald ash borer larvae have been spotted in trees on Duluth's Park Point, while a pesticide treatment that biologists hoped would drive zebra mussels out of Christmas Lake has failed to do so.

Emerald ash borers in Duluth

The Minnesota Department of Agriculture says it identified emerald ash borers (EAB) in four of the trees it sampled on Duluth's Park Point (which is across the Lift Bridge from downtown Duluth).

The invasive insect's larvae have killed tens of millions of ash trees in the U.S. since arriving from Asia, but this marks the first time the bug has turned up in northern Minnesota.

The discovery is not a surprise, since emerald ash borers were discovered in neighboring Superior, Wisconsin, more than two years ago.

Agriculture officials say they'll now begin working with the city of Duluth and St. Louis County on slowing the spread of the EAB. They took an immediate step on Friday by declaring an emergency quarantine for Park Point. That means anything that might contain EAB – particularly firewood – cannot be moved from the area.

11 counties in the Twin Cities area and southern Minnesota are already

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The News Tribune says ash trees make up nearly 20 percent of the trees along city streets in Duluth. A city official tells the newspaper all ash trees less than 12 inches in diameter will be cut down, whether they're infested with EAB or not, to help slow the spread of the pest.

Zebra mussels spreading in Christmas Lake

Like other exotic species, zebra mussels have raised a vexing question for biologists: how can we get rid of these things?

A bacteria-based pesticide that the Department of Natural Resources has used to treat Christmas Lake in Shorewood showed promise last fall and this past spring.

But the DNR announced Friday that it will stop the treatments because it's now clear that the invasive mussels are reproducing and spreading through the lake.

While the agencies involved in the Christmas Lake treatments are disappointed, the DNR says information from the experiment will help in the ongoing fight against the invasive species.

Or, as Shorewood Mayor Scott Zerby told KSTP, "It's a battle we've lost but not a war we're willing to give up on."

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