Rising from the Ashes

An odd whirl of scrawny shoots spiraling the trunk of one small tree sounded the death knell for the ash in my 10-acre woods outside of Duluth. It was late 2023, and, as I would learn, the emerald ash borers had been dining for years. By summer 2025, a grove of 80-year-old black ash stood leafless and stripped of bark by woodpeckers hunting EAB larvae.

I’m far from alone in seeing ash trees in my area die off. Across a significant swath of the state, many Minnesotans have noticed as the state’s three ash species, green, white, and black, have succumbed to this invasive bug. In cities infested by EAB, ash planted for shade have died and been removed from boulevards, yards, and parks, leaving gaping holes in the urban canopy. In public and private woodlands around the state, except for the far north and most of the far west, dead or dying ash are becoming a more common sight, scarred carcasses on the landscape.

“What we really stand to have happen in Minnesota is the functional extinction of our three ash species,” says Rachael Dube, forest health specialist for the Minnesota Department of Natural Resources. “We’ve seen nothing like this from an invasive tree killer in Minnesota. We expect to see a huge loss of forested land.”

Other tree diseases and infestations have swept through the state, including Dutch elm disease, oak wilt, and butternut canker, which have killed millions of trees. The major difference between them and EAB is that EAB has the potential to deforest parts of Minnesota’s landscape for decades.

Although EAB has been established in the state for nearly 20 years, and its effects are especially visible in infested cities, the bugs have yet to reach most of Minnesota’s billion ash trees, including vast tracts of black ash forest in the north. Research modeling predicts EAB will be found throughout the state in 15 years. “There’s no way of knowing for sure,” Dube says. “And that doesn’t mean it’ll be in every ash forest. That could take much longer.”

However long it takes, EAB is here to stay, bringing with it economic, ecological, and cultural challenges. Although a silver bullet solution seems elusive, scientists are experimenting with novel biocontrol solutions and breeding resistant trees from the less than 1 percent of ash that survive infestation. Land managers are planting alternatives to native ash, whose loss will create effects that range from subtle to landscape-altering depending on species and habitat. These efforts are an evolving push to cope with EAB while preserving the state’s natural heritage.

An Uninvited Guest. Emerald ash borer is an insect native to eastern Asia that likely reached North America as a stowaway in wooden shipping materials in the 1990s. The bugs were confirmed on this continent in Detroit in 2002, then reached St. Paul by 2009. EAB has since spread to 59 of Minnesota’s 87 counties, including six new ones in 2025. Apart from an infestation in Moorhead, far west-central Minnesota is still EAB-free, as is the state’s northwestern corner and a boreal band extending east to Lake Superior.

The insect’s destructive methods are quite simple. “Adults lay eggs in bark crevices,” explains University of Minnesota doctoral candidate Colin Peters. “Typically, the eggs hatch in late June and into July. Larvae chew into the tree and begin feeding through summer and into fall. Then they overwinter under bark.”

The wormlike larvae damage outer wood and inner bark, tissues the trees need to transfer water, energy, and nutrients between leaf and root. The larvae feed with relish on all three species of ash in the genus Fraxinus, killing more than 99 percent of the trees they infest within several years. Black ash, our most abundant species, is the most vulnerable and preferred.

The three ash species EAB attacks are distinctive, each with its own ecological value. White ash is uncommon and grows in the southern two-thirds of eastern Minnesota. Green ash grows in every county along waterways and in uplands. Green and white ash look similar, and both were popular avenue and yard trees prior to EAB.

Black ash, Minnesota’s most plentiful ash species, was seldom used in landscaping. It is found throughout the state’s forests and has blunt branches slow to leaf in spring. While it isn’t a common yard tree, black ash thrives in swamps too wet for other trees. It can form stands of pure black ash that are at extreme threat from EAB invasion.

Removal and Treatment. Jonathan Osthus tracks EAB for the Minnesota Department of Agriculture. The shiny green bugs first appeared in the state in densely populated St. Paul, in an area near major highways and a railyard. Osthus says, “As EAB spreads into areas with higher populations, it provides more opportunities for things like infested firewood to be transported to new locations.”

“EAB doesn’t typically move very far on its own,” says Dube. “Humans are the real superspreaders of EAB.”

Accordingly, the state’s biggest cities have been dealing with EAB the longest. Minneapolis finished removing its dead and dying street ash in 2022 and St. Paul in 2024, a 15-year project costing $36 million. Dead and dying ash remain in people’s yards, however, and homeowners are ultimately responsible for removing hazardous trees—which can be quite expensive. The DNR has helped communities cope with ash removal by offering grants through its Community Tree Planting and ReLeaf programs, funded by appropriations from the state Legislature.

After EAB hit Rochester in 2016, tree removal costs quickly exceeded the city budget, so Rochester opted to periodically treat 4,000 of its best ash with insecticide, which can stave off infestation.

“This is the cheapest alternative and still allows the city to realize the canopy benefits,” says city forester Jeff Haberman.

Dube points out that treatment can be expensive for landowners “because you’ll have to do it for the life of the tree, and costs add up.”

A silver lining with EAB is that cities are planting more diverse trees. Duluth city forester Clark Christenson is replacing boulevard ash with 45 different species, including swamp white oak, river birch, yellowwood, black haw, and sycamore.

“We’ll plant two species on each side of the road, four species per block, then change species on the next block,” he says. “In the future if we have a pest or issue, any block would be losing at most one quarter of its trees; that means a neighborhood will lose only 5 to 8 percent of trees at most.”

Science to the Rescue? Researchers are testing ways to use wasps or fungus as biocontrols to combat EAB. After the emerald ash borer appeared in the United States, scientists went to Asia to find its natural predators. They returned with several species of parasitic wasps. Osthus says testing found that the wasps prey only on EAB, and without EAB they would not survive.

“These wasps are very small,” Osthus says. “Humans won’t come into contact with them or recognize them—they’ll look like a gnat.” Three Asian wasp species were released in Minnesota beginning in 2010.

One of them, Tetrastichus planipennisi, says Osthus, “lays its eggs inside the EAB larvae, where the wasp larvae hatch and consume the EAB larvae from the inside out.” The wasps, however, “are not going to protect the large mature trees on the landscape right now. It’s really a bet on the future. After EAB moves through an area, the wasps may suppress that population enough to allow ash trees to exist.”

This summer, University of Minnesota scientist Colin Peters will field-test three species of EAB-killing native fungi. Like the wasps, the fungi are unassuming.
“To the average nature enthusiast, you would never come across these,” Peters says.

In lab testing, the deadliest fungus killed all the EAB adults exposed to it after a week. (EAB adults live three weeks.) Although the fungi are already present in the environment, they infect just 1 or 2 percent of EAB. Peters aims to raise infection rates by deploying slippery-sided traps that force EAB adults into contact with fungi before releasing them. He foresees placing hosts of traps each summer along EAB’s spreading front.

“We don’t view fungal biocontrol as a silver bullet,” he says. “It’s an additional tool. We’re trying to reduce the population enough that our ecosystems can reach a balance.”

Reshaping the Landscape. The state’s southeastern woods saw the second wave of EAB move into Minnesota, and most of the southeast is now broadly infested. In much of the state, however, EAB is just beginning to penetrate forests, particularly in the north, where fewer people, geographical isolation, and colder climate help to slow their spread. In southern Minnesota, the EAB life cycle—from egg to adult—can take just a year. The life cycle in the colder north typically requires two years. Additionally, sustained -30 temperatures can kill 90 percent of EAB larvae, though climate change is making these cold spells less frequent.

So far only 2 percent of ash on state land, which is mostly in the north, is infested, meaning there’s still opportunity to slow EAB’s spread and to anticipate effects from widespread die-offs.

“There are going to be a lot of unknown ecological impacts,” the DNR’s Dube says, mentioning that 43 species of native insects and arachnids rely on North America’s ash trees. Mammals, birds, reptiles, and amphibians, even understory vegetation will be affected by the ash’s absence. Dube worries about invasive plants overtaking forest openings created by EAB.

Black ash are scattered throughout the state’s forests but become copious in northern wet woods, a forest type characterized by saturated soils, low tree diversity, and plant and animal life uniquely adapted to this environment. The loss of these forests will have a dramatic effect.

“Black ash can live with flooded roots,” says Chris Gronewold, DNR silviculture program coordinator. “It has special adaptations to allow gas exchange from below flooded ground. There isn’t another species in Minnesota that uses this adaptation to that extent.”

“Black ash trees act as straws, sucking up water in wet areas,” says Dube. Groundwater is released through their leaves as vapor. Without the trees acting as evaporators, groundwater is expected to rise in areas dominated by black ash.

“We anticipate many of these areas could convert into marshes and brushlands,” Dube says. “We may see large swaths of forest permanently gone.” Dube predicts wet black ash forests could be replaced by cattails, alders, and invasive reed canary grass.

Not all black ash woods are so wet, and the drier ones will be succeeded by trees like aspen, balsam, and maple, but the black ash die-off will be huge. Black ash compose 9 percent of the state’s forests.

“We have more than a million acres of black ash in northern Minnesota,” Dube says. “That’s about the size of the Boundary Waters Canoe Area Wilderness. It would be like canoeing from one end of the Boundary Waters to the other”—a span of 150 miles—“with the whole thing filled with dead ash trees.”

Tree by Tree. While EAB spreads, organizations are adapting to the new reality. The DNR, Dube says, has been planting supplemental native tree species, including balsam poplar and white cedar, on 650 acres of black ash–dominated forests. Gini Breidenbach works with the nonprofit Minnesota Land Trust, which is reforesting ash lowlands in Duluth parkland along the St. Louis River. When a survey found 169 bird species used these woods, “That was a motivator for me to get this project underway—to make sure those wet forests still exist for the avian community,” Breidenbach says. “We could spend years trying to find the perfect solution, or we can plant tree species that we suspect will grow and that are native, and get a head start.”

Since 2022, the Minnesota Land Trust has planted 77,000 trees on 159 acres.

The Fond du Lac Band of Lake Superior Chippewa, on its reservation near Cloquet, began planting trees in preparation for EAB in 2008. The Band is one 11 tribal nations that share geography with the state of Minnesota. Native plants are ingrained in Indigenous language and culture. The Ojibwe word for ash, aagimaak, means “snowshoe wood.”

“Having ash in the future is super important for us,” says Madison Bear, invasive species manager for the Band’s Natural Resources Department. Bear says other trees, like hackberry, are proving to be decent substitutes for crafts like lacrosse sticks, cradle boards, and “snow snakes” used in a winter game. For basketry, though, Bear says, “Nothing compares to black ash.” Black ash has a unique quality that allows artisans to peel away annual growth rings into flexible strips used for weaving.

Across the road from Bear’s office, Band member John Roterman is working at the Fond du Lac Museum. Roterman points out three large black ash baskets made 80 years ago. He says, “These traditional activities our ancestors have been doing on these lands for thousands of years, it’s really important to teach the next generations.”

“It’s a way to preserve culture,” adds Bear.

EAB arrived on the Fond du Lac Reservation in 2024. Alex Mehne, forest manager for the Band’s Natural Resources Department, is embracing “assisted migration,” which means planting trees not presently found on the reservation.

“The forest is like a bookshelf,” Mehne says. “Assisted migration is maybe a screw that holds shelves together.”

He hopes trees from farther south will close ecological gaps created by dying ash. In one recent planting, Mehne supplemented native white cedar and tamarack trees with river birch (“from two counties south”) and American sycamore, which grows in Iowa. In 2025, the Band planted 100 blue ash from southern Michigan. Blue ash is native to the central United States and survives EAB at much higher rates than local ash. Blue ash may support ash-dependent native insects and provide materials for cultural practices, though they’re untested against northern Minnesota winters.

Both Mehne and Dube expect ongoing projects propagating seedlings from the less than 1 percent of white, green, and black ash that survive EAB invasion will eventually produce resistant ash.

“We keep reminding people to please, please don’t move ash around,” Dube says. “It gives us more time to develop these tools to help protect these forests.”

An Underrecognized Problem. January 2026 brought -30 lows to northern Minnesota that will set back EAB populations. Wasp and fungal biocontrols may check future EAB waves and help survivor ash to regenerate. Early ash replacement plantings will show which trees succeed. And property owners are fostering resilient forests, sometimes with help from a DNR cost-sharing program for woodland stewardship. Statewide, 61 percent of black ash forests are privately owned, including my home woods.

These are all positive developments, but the fact remains that most ash trees in Minnesota will not survive EAB—an outcome that Dube believes is underrecognized by the public.

“I think that the loss we are going to experience of black ash in northern Minnesota, I don’t know if people are really ever going to fully appreciate it,” says Dube. “A lot of ash forests are—they’re swamplands, they’re not places where people are tromping around a lot or even recreating in a lot.”

When EAB killed off the ash trees on my northern Minnesota property, I gained a new appreciation for the damage these bugs can do. After the infestation, I felled dozens of trees ranging in width from telephone pole to thumb. It was hard, slow work. I split the logs for firewood that I burned on-site; I heaved branches into piles and burned the piles when snow covered the ground.

In spring I planted cedars, oaks, cottonwoods, tamaracks, and maples on the fire scars. In May when the berry trees bloomed and flocks of warblers flitted through the aspens, the seedling trees unfurled new leaves that reached hungrily toward the sun.