In 2009, an invasive tree pest was discovered on an ash tree in St. Paul. This past fall, 15 years later, the city cut down its last ash tree.
While St. Paul and other more populated cities have been aware of the emerald ash borer for some time, many Greater Minnesota cities are more recently learning about the pest and facing the challenges it brings their communities.
Restrictions on moving wood have helped contain the ash borer’s spread, but spread along transitways, mainly through human traffic still persists.
This past summer, the city of Glenwood in the southwestern part of the state faced its first emerald infestation on an ash tree. Pope County went under “quarantine” per state rules and then the city later conducted an inventory of the ash trees in the area to get a sense of what might be the fallout.
What they found was approximately 978 ash trees in public areas. Of those, roughly 40% were in the “fair, bad or dead” category, according to city administrator David Iverson.
“We have to make some decisions of what we’re going to do with regard to these trees,” Iverson said. “Do you start taking them down or not? And what we’re finding is it sounds like … dead trees are tougher to take down because their branches drop off and they fall around, versus a healthier tree is easier to take down than a dead tree.”
But resources are limited. Glenwood is looking for funding sources for this because if it doesn’t find something, Iverson said there’s a high chance the city would have to do some restructuring of other city projects. Taking down a tree he estimates costs around $1,000 per tree, and that doesn’t take into account replanting.
“It’s one thing to take down trees, but it’s somewhat unrealistic to think a city our size is going to be able to pay if you were going to take down, say, 100 trees, and take down half of these trees we have in four or five years,” he said. “I just don’t know how some of these small towns are going to be able to come up with funds to do this because there’s always only so much money. So, I have a feeling we are going to have to look to … nibble down the size of some of these other street projects that we look to try to do or forgo a project for a year and just jump on a bid to take down a number of trees and just use the money that way.”
The League of Minnesota Cities (LMC) is pushing for more state funding for communities struggling with the emerald ash borer. It’s not an issue that’s leaving anytime soon, said Craig Johnson, the senior intergovernmental relations representative for the League of Minnesota Cities.
According to Johnson, there’s significant cost in doing an inventory to find out where ash trees are and their state of health. A concern is the tree becomes more hazardous as it gets more infested.
“Ash trees get so brittle when they die that they can literally explode. A six-inch branch can just shatter from even a bird landing on it,” Johnson said. “They are definitely a public health and safety issue. If you have emerald ash borer, and there’s a tree that looks like it’s starting to die, it has to be removed or it is going to start falling on people and cars and houses.”
There’s an element of timeliness in finding a solution for these communities, but it has to still be financially viable. Iverson said as soon as Glenwood found out about it, city workers strapped in their boots.
“We have a very green community with a lot of trees, which we really enjoy … and it’s the pride of our town,” Iverson said. “You hate to see the loss of all those trees, but yet, if it’s there, you’ve got to do something. We just cannot sit on our hands.”
LMC has sought funding in past years to give communities with emerald ash borer infestation priority on the state’s money to help with the response, like the community tree-planting grant program, established in 2024 to prioritize projects for communities with emerald ash borer infestations. In the 2023 session, the DNR received funds for a “ReLeaf” program, with around $16 million during that biennium dedicated to grants to help communities with removal and tree planting. In subsequent years, a recurring $400,000 will be granted to the program, which LMC fears might get cut into with a tighter budget.
“This year, the budget is going to be extremely tight, and there are going to need to be cuts to the budget, not adding new spending to the budget,” Johnson said. “We are going to be working pretty hard to make sure that the emerald ash borer funds that are in place stay there and that where possible, we reallocate some other funds to provide more resources there, because every year more and more cities are having emerald ash borer hit.”
Different approaches to the borer
When dealing with the emerald ash borer, St. Paul opted to get rid of all its ash trees, while Minneapolis took a different approach, targeting at-risk trees and removing those while treating the bigger healthier trees.
Angela Gupta, an extension educator at the University of Minnesota, said the federal government for a long time supported the Minnesota Department of Agriculture’s (MDA) emerald ash borer surveilling, but it’s no longer a federal priority. MDA still has strict quarantine rules, like policies to limit the spread of firewood in certain areas, which Gupta said is why it’s taken this long for the bug to get to infest some areas of the state.
“The idea with a quarantine for emerald ash borer is, if you have emerald ash borer in an area, you want to retain it only in the area and don’t let it get out of that area,” she said. “That’s been pretty successful. So part of that is buying time. If we can buy time for science to come up with ways in which to manage emerald ash borer or to mitigate the damage, then we may be protecting our resource.”
Gupta said there are good options for treating the trees now, which can pay off for communities where the concentrations of the pest are low. Treating is a good option for trees that haven’t lost too much of their canopy yet. But if a tree has lost more than 30% of its canopy, it’s likely too late to treat, according to Gupta. For trees near an infestation, Gupta said it’s recommended to treat if it’s within a 10-15 miles radius.
She advises if a community has to cut down trees, they replant them with a variety of species so they don’t end up in a similar situation down the road.
While Minnesota has been at controlling the spread of the infestation, in recent years even despite quarantines, it has gotten harder to contain the spread, one reason for which is climate change, Gupta said.
Temperatures of negative 30 degrees Fahrenheit will kill 90% of the insect, studies show.
This past winter, when temperatures were warmer and there was no snow, conditions were ideal for the ash borer to survive and spread. The emerald ash borer is now being found in areas it wasn’t before, like the Chippewa National Forest in northern Minnesota. In areas of the state, like some spots in northern Minnesota, places that previously remained safe from the pest, due to temperature, quarantine rules and other factors, black ash trees may now be more at risk.
“Emerald ash borer will be able to benefit as we get warmer,” Gupta said. “That’s a concern because Minnesota is the state with the largest ash resource in the United States at this point.”
Ava Kian
Ava Kian is MinnPost’s Greater Minnesota reporter. Follow her on Twitter @kian_ava or email her at akian@minnpost.com.
