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Ash borer threatens trees on Twin Cities' U campuses

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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 www.forestryimages.org

Up to 1,300 ash trees on the Twin Cities campuses of the University of Minnesota could eventually die from the invasive emerald ash borer, whose larvae destroy the trees' ability to transport water and nutrients.

Plans are in place to remove and replace the trees before the emerald ash borer kills them. But the discovery this week of an infested tree on the university's St. Paul campus means the beetle's known range in the state has grown larger since officials first found the emerald ash borer in May.

"This is the furthest away from that core area that we've found an actual infestation," said Geir Friisoe, director of the Minnesota Department of Agriculture's plant protection division. 

Officials have tried to control the spread of the emerald ash borer in several ways, including by removing infested trees, telling people not to move firewood, and setting up ash borer traps to monitor the spread. Friisoe said those efforts will continue, but he said there's only so much that can be done to slow the spread.

"As you get further away from that core epicenter, it gets much more difficult," he said, adding that he believes there could be more trees within a one to two-mile radius of the original infestation, which was found in St. Paul's St. Anthony Park neighborhood.

At the University of Minnesota, plans are in place to remove and replace most of the ash trees in the next seven to 10 years, said grounds superintendent Les Potts. This year, up to 15 percent of the ash trees on the Minneapolis and St. Paul campuses will be removed, he said.

Potts said he expects it won't be easy for the campus community to see so many trees go. 

"Anytime we take a tree down on campus, people notice."

"My experience is that anytime we take a tree down on campus, people notice," Potts said. 

The infested tree on the St. Paul campus looked fairly healthy, but a beetle was found in a purple sticky trap that had been placed in the tree. When agriculture officials removed some of the tree's bark, they found emerald ash borer. They also located woodpecker holes, which is another sign that a tree could be infested.

Because the St. Paul campus is within Falcon Heights, city officials are moving forward with plans to remove and replace about 300 ash trees on boulevards, said City Administrator Justin Miller. 

The Falcon Heights City Council is scheduled to vote Wednesday night on a plan to remove and replace those trees over a seven-year period, he said. 

"It's really going to change the landscape," Miller said of the tree removal, adding that city officials are already planning to plant many different types of trees. Right now, ash make up about 30 percent of the boulevard trees, Miller said.

"We don't want to make the same mistake of planting an entire block with the same type," he said.

  Other cities throughout the state face the same problem, because many cities planted ash to replace elm trees killed by Dutch elm disease. 

The state Legislature has made $2 million available for cities to respond to the emerald ash borer. Half of the money will go to cities already dealing with infestations, and the other half is for cities to develop removal and replacement plans for their ash trees, Friisoe said. 

Cities must apply by the end of this week for the grants, which will be awarded in January, he said. 

The Minnesota Department of Agriculture also expects there will continue to be federal money available to detect the beetle and educate people about how to identify symptoms of an infestation. 

The state has about 2,000 sticky traps set up throughout the state to detect any further spread, Friisoe said.

Emerald ash borer was first found in the state in May in a neighborhood in St. Paul, not far from the intersection of Interstate 94 and Highway 280. Since then, officials have found the invasive beetle in another St. Paul neighborhood about a half mile away from the first.

The ash borer has destroyed millions of trees in more than a dozen states.