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BRIMSON, Minn. 鈥� As wildfires spread north of Duluth earlier this month, updates from fire officials on the largest two 鈥� Jenkins Creek and Camp House fires 鈥� often included a line noting the fire was burning through 鈥渁 landscape heavily impacted by the spruce budworm.鈥�

A large outbreak of the eastern spruce budworm 鈥� a caterpillar native to the region that feeds off balsam fir and white spruce trees 鈥� is defoliating the trees and stressing or killing them, which can then help fuel wildfires.

Last year, the budworm affected some 712,000 acres, or 1,100 square miles, of Minnesota forests, almost all in the state's Arrowhead region, the largest area since 1961, according to Eric Otto, a forest health specialist for the Minnesota Department of Natural Resources in northeastern Minnesota. If you look at the last four years, it鈥檚 affected almost twice that area, according to the DNR鈥檚 most recent

Northland Outdoors

In Minnesota鈥檚 Arrowhead, balsam firs ravaged by spruce budworm outbreak ramp up fire fears

The native insect that feasts on the short-lived conifers has exploded throughout much of the state鈥檚 northeastern region at a level not seen since 1961

Mar 12

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By  Mike Mosedale / MinnPost

鈥淪pruce budworm, currently, is probably one of our biggest forest health issues, especially in regards to the amount of acres it damages each year,鈥� Otto said.

In its caterpillar form, the spruce budworm eats away at the needles of white spruce and balsam fir. (Despite its name, it prefers 鈥� and does the most damage to 鈥� balsam fir.) Then, as a moth, it lays its eggs on the needles of those trees.

Gary Meader / Duluth Media Group

An outbreak in a specific area can last 6 to 10 years, which is about as long as the trees can withstand the budworm鈥檚 feeding, according to the DNR.

Otto said that when that food source is gone, the budworms move to an adjacent area, causing an outbreak there. After a 30-to-60-year cycle, they鈥檙e back at that first area.

Contributed / Kyle Stover, USDA Forest Service

That鈥檚 about as long as it takes the balsam fir in the understory to mature, replacing the trees that died in the last outbreak, and for the budworm population to take over again, said Anna Stockstad, an extension educator focused on forest ecosystem health with the University of Minnesota Extension.

Otto said the region last saw an outbreak in the 1990s.

Budworm or not, balsam fir is good at spreading fire thanks to its flammable needles, low branches and resinous bark, Otto said.

Those properties act as a ladder fuel, spreading flames from the forest floor to the canopy, where trees otherwise resistant to low-intensity fires can catch fire.

Gary Meader / Duluth Media Group

鈥淓ven if we didn鈥檛 have this spruce budworm outbreak, with the way the forest is composed, we would probably still have these fires,鈥� Otto said, noting the fires were likely human-caused, during exceptionally dry and windy conditions.

But, Otto said, the budworm outbreak probably altered the fire behavior, as dead balsam fir are particularly dry in the spring, some 5 to 8 years after dying from budworm. It isn鈥檛 until 10 years or so after the balsam firs die that they start to decompose, increasing their moisture content.

There鈥檚 now an overabundance of balsam fir, the budworm鈥檚 preferred meal, thanks in part to fire suppression during the 20th and 21st centuries, Stockstad said.

Without regular, low-intensity fires clearing a mature forest鈥檚 underbrush, where shade-tolerant balsam firs thrive, the tree species can build up.

鈥淪o this means we have a lot of dense mature balsam fir on the landscape, which is just like candy for spruce budworm,鈥� Stockstad said. 鈥淎nd so when we have more of the food source for spruce budworm, we鈥檙e going to see higher population in spruce budworm itself.鈥�

As the region鈥檚 paper mills have shrunk or closed, so too has the market for balsam fir in northeastern Minnesota.

The closure of Duluth鈥檚 Verso paper mill in 2020 left UPM Blandin in Grand Rapids as the last mill buying fir in the region, but it鈥檚 too far from the budworm outbreak, Otto said.

Contributed / Eric Otto, Minnesota Department of Natural Resources

While some loggers can bring balsam chips to Minnesota Power鈥檚 Hibbard Renewable Energy Center in Duluth, which burns wood waste to produce electricity, Chris Dunham, the Nature Conservancy鈥檚 associate director of resilience forestry in northeastern Minnesota, said that 鈥渄oesn鈥檛 match the demand in any way, shape or form.鈥�

Still, Stockstad said landowners should consider removing dead balsam, which could be chipped, piled to make wildlife habitats, or, under the right conditions, burned.

Then, landowners can start to consider planting other species of trees.

Foresters don鈥檛 want to eliminate balsam fir 鈥� or even budworms 鈥� altogether. Instead, they want more of a variation of tree species, particularly those that can survive low-intensity fires and withstand a warming climate.

Dunham and the Nature Conservancy, which partners with government agencies and private landowners, are in the midst of planting 2.5 million trees in northern Minnesota this year. Species include red oak, bur oak, white cedar, yellow birch, tamarack, black spruce and white pine.

鈥淒iversity is the superpower of the forest,鈥� Dunham said. 鈥淭hat鈥檚 what enables us to hedge our bets against what is likely coming down the pike. We want to be diverse so that if there鈥檚 something that affects another species, we鈥檙e not just putting all our eggs in one basket.鈥�

But planting millions of trees is just the first step.

Dunham said crews then must monitor and maintain planting sites for 7 to 10 years to make sure they survive, by pruning for blister rust, clearing brush and guarding against deer.

White pine and white cedar are 鈥渁bsolutely beloved by deer,鈥� Stockstad said, making it hard to establish those species without fencing and other protection. Meanwhile, balsam fir is not a preferred browse species for deer, allowing the tree species to flourish.

鈥淲e can鈥檛 just cut it and walk away,鈥� Dunham said. 鈥淚t鈥檚 going to take some intervention and investment.鈥�