Bugs, blowdowns last year heighten Minnesota wildfire worries
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High winds and tree pests did extensive damage to forests last year across Minnesota, and that's raising concerns about the coming wildfire season.
Nearly 24,000 acres of forest were damaged by wind last year, with nearly half of that coming from the derecho that swept across the Bemidji area last summer, according to the Minnesota Department of Natural Resources’ recently released 2025 forest health report.
It's the most wind damage seen in a single year since 2011.
DNR forest officials say teams salvaged damaged timber on state-managed land in the blowdown area. But other locations with downed trees haven’t been cleared.
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“There are still a lot of smaller parcels and isolated pockets of blowdown that may or may not ever get cleaned up, and those are the risks going into the future,” said Ben Lang, a DNR forester.
Downed trees provide more fuel for wildfires, making them burn more aggressively.
“They're going to be hotter,” said Lang. “They're going to be trickier to deal with because access and maneuverability around and in those fires is going to be trickier.”
Officials estimate the fire risk in the Bemidji area will be elevated for the next three to five years.
The fire risk assessment comes from the DNR’s annual forest health report for 2025. The report includes information about the impacts of extreme weather and invasive organisms on Minnesota forests.
Bugs take a toll
Insect infestations in northeastern Minnesota continue to raise the fire risk for a vast swath of forest damaged by a native caterpillar.
In May, wildfires near Brimson scorched an area about the size of Minneapolis. The blazes were made worse by spruce budworm, a North American moth whose caterpillars feed on the needles of balsam fir and white spruce.
The DNR says spruce budworm defoliated at least 182,000 acres of forest last year. The actual acreage of damage is likely much higher, but smoke from Canadian wildfires last summer made it difficult for the DNR to map out the extent of harm caused by the caterpillar.
“Even though spruce budworm didn't start those fires, it certainly helped them burn hotter and faster than if spruce budworm wouldn't have affected the forest,” says Brian Schwingle, forest health program coordinator for the DNR.
Other takeaways
The DNR report says the status of oak wilt is generally stable.
There are no signs that the fungal pathogen has spread beyond the 33 Minnesota counties where it has been found. However, additional outbreaks of oak wilt were detected in already affected Morrison and Pine counties.
The fatal oak disease has spread slowly northward in Minnesota since the 1940s.
Emerald ash borers continue their spread across the state showing up in six new counties, bringing the total number of impacted counties to 59.
Emerald ash borers were first found in the state in 2009 and currently occupy roughly a quarter of Minnesota. These small green insects cut off the vascular system of ash trees, disrupting their ability to take in water and nutrients.
“We expect that emerald ash borer will continue to spread throughout Minnesota over time,” said Schwingle, “We have a lot of ash trees.”
A couple of unusual pests caused tree damage in northeast and northwest Minnesota.
The green-striped mapleworm, which is rare in Minnesota, made a surprise appearance in Ely, where it was found feeding on the leaves of red maple trees.
Additionally, a few acres of young aspen trees in Marshall County were defoliated by a sawfly species that hasn’t been recorded by any of the DNR’s annual reports, which date back to 1969.
Schwingle says in both cases, the damage was not concerning and only affected a very small area.
