In a surprise to nobody that's been paying close attention, emerald ash borer has reached the local area.

The Minnesota Department of Agriculture announced Tuesday that Nicollet and Redwood were the latest counties with EAB discoveries, and emergency quarantines were put in place on wood movement. Thirty counties have now reported EAB, including neighbors Sibley, Brown, Rice and Blue Earth counties. There have been no discoveries in Le Sueur County, meanwhile, but it is almost completely surrounded by counties with sightings.

11.25 Emerald Ash Borer Nicollet County

Jonathan Osthus, emerald ash borer technical assistance coordinator with the Minnesota Department of Agriculture, spotted this ash tree infected by EAB along Hwy. 15 on the west side of Nicollet County. This was the first identification of the insect in the county. (Photo courtesy of Jonathan Osthus)

"There are a couple counties, like Le Sueur County, that are completely surrounded, and we’re doing our best to survey those areas," said Jonathan Osthus, EAB technical assistance coordinator with the MDA.

Osthus explained that he was on his way to check a known EAB site in Springfield when he noticed signs of the insect's presence on ash trees along Hwy. 15 in Lafayette Township, western Nicollet County. MDA staff were able to find live EAB larvae and collect samples for federal identification.

"Last week, I was doing some visual surveys throughout that area," Osthus said. "There was a report from a tree care specialist in Springfield where it had already been identified. On the way there, I noticed some trees along Hwy. 15 with excessive woodpecker holes, and I stopped over and noticed the signs of EAB. The woodpeckers will sort of strip at the bark and make the tree look a bit blonde. The winter time is actually the best time to look."

The sighting was near New Ulm on the opposite side of Nicollet County from St. Peter. However, Osthus noted that it can take up to three years before EAB's presence shows in ash trees, and while he wasn't going to speculate, he said it certainly could already be in St. Peter.

"By the time you see evidence, you’re already behind," Osthus said.

11.25 Emerald Ash Borer Nicollet County 2

This map from the Minnesota Department of Agriculture will soon be updated to highlight Nicollet County as one of those where emerald ash borer has been spotted. Le Sueur County is now almost surrounded by counties where EAB has been spotted.

Emerald ash borer larvae kill ash trees by tunneling under the bark and feeding on the part of the tree that moves nutrients up and down the trunk. Often, the trees show several signs of infestation because of this. Woodpeckers like to feed on EAB larvae and woodpecker holes may indicate the presence of emerald ash borer. Also, the EAB tunneling can cause the bark to split open, revealing characteristic S-shaped galleries underneath. It was first spotted in Minnesota in 2009.

11.25 Emerald Ash Borer Nicollet County 3

Nicollet County contains a high number of ash trees compared to much of greater Minnesota.

There are about 1 billion ash trees in the state of Minnesota. They were heavily planted in communities across the state in the 70s, 80s and beyond after many Elm trees were devastated by Dutch Elm disease. They are also common in natural settings. 

Tree experts, like those at MDA, are encouraging communities to diversify their tree programs now, becoming less reliant on the ash, but they also hope to buy time, in order to better stave off the invasive insect. 

"We hope to maintain and keep ash in the natural ecosystem," Osthus said.

Reach Regional Managing Editor Philip Weyhe at 507-931-8579 or follow him on Twitter @EditorPhilipWeyhe. ©Copyright 2021 APG Media of Southern Minnesota. All rights reserved. 

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