Ash trees marked; fate is up in the air

For now, the bright green sashes encircling city ash trees are there to identify them as vulnerable to emerald ash borer - not to mark them for imminent destruction. But destruction is coming, whether by a preemptive strike by a chainsaw or death over time due to the bright green invasive insect.

"It means it's an ash tree, that's all," said public works director Caleb Peterson. "What we will end up doing is yet to be determined."

Emerald ash borer (EAB) is an insect that attacks and kills ash trees. The adults are small, iridescent green beetles that live outside of trees during the summer months. The larvae are grub or wormlike and live underneath the bark of ash trees. Trees are killed by the tunneling of the larvae under the tree's bark. EAB spreads through short-distance natural flight and long-distance transport of infested firewood. The invasive insect was first discovered in Cloquet in April 2022 and in Esko and the Fond du Lac Reservation earlier this year.

Peterson said about 300 ash trees have been identified so far in Cloquet boulevards and parks.

"It doesn't appear that many are infested so far," he said.

The city of Cloquet cut down just over 30 infested ash trees this winter - marked with a large pink X - before the ash beetle could emerge in the spring. Those trees will be replaced with a different variety.

Many cities have chosen to cut down all their public ash trees before the beetles can kill them.

City workers in St. Paul started cutting down and replacing 26,000 ash trees in 2009 and celebrated finished the job three months ago. In total, they cut down one-fifth of the urban canopy, according to a MinnPost column by Bill Lindeke, a lecturer at the University of Minnesota.

There are now 53 counties in the state with known EAB infestations.

The city of Cloquet is getting financial help with its EAB response through a $428,000 grant for community forestry work from the Minnesota Department of Natural Resources. As part of the DNR grant process, the city is working with a certified arborist to inventory all city-owned trees and put together a management plan that will identify best practices for years to come. The city is also partnering with staff from the Fond du Lac Band of Lake Superior Chippewa and the Carlton County Soil and Water Conservation District.

The green ribbons visible around town now identify the public ash trees and offer a QR code and website (www.cloquetmn.gov/departments/news-information/emerald-ash-borer) for more information about EAB and the city's ongoing programs. The webpage also links to an SWCD brochure outlining different EAB resources and 16 options for replacing infested ash trees.

The city or its contractors are not marking trees on private property, but homeowners are encouraged to identify if they have ash trees on their property and prepare for any needed mitigation.

"Just because you see a ribbon on a tree it doesn't mean it will be cut down in the next year or even the next five years," Peterson said. "But I'm sure over time most of them will go away."

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Emerald ash borer signs

• Woodpecker activity is a top sign of tree infestation, as well as S-shaped feeding marks left under the bark of a tree.

• Damage to a tree will be found mid-trunk and higher.

• It can take about five years for a tree to die after being infested.

• Residents who have questions about EAB or identifying at-risk ash trees, or concerns about a tree becoming a hazard and if it needs to be removed, can contact Cloquet engineering technician and project manager Joe Hafner at 218-655-1512 or [email protected].