Hope they Fried

How a worm perpetuated wildfires in northern Minnesota
Experts say an outbreak of spruce budworms has helped sustain wildfires north of Duluth.

By Kyeland Jackson

The Minnesota Star Tribune
May 14, 2025 at 6:41PM
Spruce budworm defoliation and mortality shown in Lake County in 2023.
Spruce budworm defoliation and mortality shown in Lake County in 2023.

Wildfires are burning through thousands of acres of forest in Northern Minnesota damaging buildings and forcing residents to evacuate their homes.

The yet-to-be-contained Camp House fire, Jenkins Creek fire and Munger Shaw fire have a small accomplice to thank for their continued destruction: spruce budworms, a well-known pest that has terrorized Minnesota forests for at least half a century, killing trees and making them more susceptible to fire.

The fires’ other helper? Humans.

“Spruce budworm’s largest impact, in my opinion, is that it can help perpetuate dense stands of balsam fir on the landscape that are fire prone,” said Mike Reinikainen, a silviculture program consultant with the state’s Department of Natural Resources’ forestry division.

Much of the area was infected by spruce budworms, whose infestations worsened the Greenwood fire near Isabella, Minn. in 2021.

What is a spruce budworm?
Typical feeding damage from spruce budworm on a fir.
Spruce budworms infected more than 700,000 acres of Minnesota forests last year.
The spruce budworm is a forest caterpillar that feeds on tree leaves until they are able to transform into a moth. Those moths lay around 10 egg masses, which can hold more than one budworm, before dying within a year. The worms are a crucial food source for predators like the Cape May warbler and purple finch, and they often drop balsam fir seedlings that help repopulate forests.

After they hatch, spruce budworms larvae can defoliate mature trees like balsam fir and spruce until they are killed.

Humans’ work to suppress fires may have also exacerbated the budworms’ growth, according to the DNR’s 2024 Forest Health Annual Report. Stopping natural fires allows fir and spruce forests to grow older and denser, which means more food for budworms.



“When there’s a forest fire that’s starting on the ground, say on the grass, the fire can move up into the canopy of the woods via balsam fir, kind of like it‘s climbing up a ladder,” said Sarah Waddle, an educator for the University of Minnesota Extension program. “And there’s a lot more balsam fir in the woods than there would have been pre-settlement of this region.”

Now fires are happening on larger scales than what might have occurred if they were allowed to happen more naturally.

When did it get here?
Spruce budworm populations rise and fall in the state every 25-40 years, but their outbreaks can last up to a decade.

Observers have tracked budworm activity every year in Minnesota since 1954, but Waddle said the bugs have been native to Minnesota for “many hundreds, thousands of years.”

Data from the DNR suggests the current outbreak began around 2020.

Where are they?
Spruce budworms outbreaks have been reported in Lake County, Cook County and St. Louis County. The insects infected more than 700,000 acres of forest last year, marking the largest impact recorded since 1961.


“Over 90% of spruce budworm damage in the last 24 years has occurred in these counties,” Reinikainen continued.

So what can people do?
Waddle advised people with infected trees to cut them down. Doing so helps the wood decompose and can become shelter for animals.

Plant trees besides the Balsam Fir to diversify what plants they can go after. And for professional help, contact your local soil and water conservation district or DNR stewardship forester.

Tim Harlow and Jana Hollingsworth of the Minnesota Star Tribune contributed to this story.

In north central Minnesota we have had a fungus killing he Black Spruce,it always something.

I think the public perception is that the budworms kills all these trees, and these dead trees create this fire hazard which leads to fires like the Brimson fires and the Greenwood fire.

I've been a bit skeptical of that since observing the aftermath of the Greenwood fire (around my cabin the fire didn't even burn into the dead balsam stands). Not that it wasn't a factor, but the extreme drought was probably the biggest thing.

The DNR guy in the article says the budworm leads to dense stands of balsam fir and that's the problem. So it's sort of an indirect connection.

A healthy balsam fir will go up like gasoline if fire gets to it. So if you have an understory of balsam fir, watch out. Doesn't matter if they are healthy or not.

Not saying that it's not a factor--having piles of dead trees lying around can't be helpful. Really, I think the biggest factor was the almost unprecedented fire conditions for early May.

Interpreting an article organized and written by the Strib is always a challenge.

I usually don’t notice too much when portaging a canoe. But yesterday while waiting out the rain I walked back up the portage and noticed 1000s of dead trees. I could barely find one spruce or balsam tree that was alive.

egknuti: "I usually don’t notice too much when portaging a canoe. But yesterday while waiting out the rain I walked back up the portage and noticed 1000s of dead trees. I could barely find one spruce or balsam tree that was alive. "

The dead trees have almost or no moisture content and will burn real fast.

I've been cutting and burning dead and dying balsams on my property north of Two Harbors for 7-8 years. It took about 4 years of annual defoliation of new needles to kill these (as well as a lot of white spruce). I finally feel like my house/garage and pines stands are "safe" after removing several hundred trees. Dry balsam burns HOT, and many areas have huge numbers standing and downed, dead balsams waiting to burn.

In all honesty, fire is the best way to remove these over vast areas. Under all those dead balsams is a sea of balsam seedlings that will grow into another massive food source for budworms down the road.

I've been replacing balsams with red and white pines, cedars, and some oaks.

Wow, they even went after the tough needles of white spruce.

arctic: "I've been replacing balsams with red and white pines, cedars, and some oaks. "

Hey arctic, have you had luck with the replacement trees so far? How are you protecting them? I've started something similar - cutting dead balsams and filling in with pines, cedars, and maples - but am only now a couple of years into this journey. I am finding that any seedlings not caged get eaten. I even have a trail cam video of a couple of coyotes playing with a tree seedling that they ripped out and used like it was a toy. Also curious - why oak and does it otherwise occur nearby your property? Is the oak for biodiversity and protection against climate change?

Spruce worm video

good read and map

DTrain: "

arctic: "I've been replacing balsams with red and white pines, cedars, and some oaks. "

"curious - why oak and does it otherwise occur nearby your property? Is oak for biodiversity and protection against climate change?"For me yes for both reasons. I have property in the Superior Highlands ecosystem where a lot of maples and yellow birch already grow. Natives have planted acorns in the area in the past, and that is why you may find stunted oak in the BWCA. The Red Oak seedlings I planted at least 10 years ago are doing great.

DTrain: "

arctic: "I've been replacing balsams with red and white pines, cedars, and some oaks. "

"curious - why oak and does it otherwise occur nearby your property? Is oak for biodiversity and protection against climate change?"

For me yes for both reasons. I have property in the Superior Highlands ecosystem where a lot of maples and yellow birch already grow. Natives have planted acorns in the area in the past, and that is why you may find stunted oak in the BWCA. The Red Oak seedlings I planted at least 10 years ago are doing great.