top of page

PESTS ARE A REAL NUISANCE

SPRUCE BUDWORM IN MINNESOTA

The Eastern Spruce Budworm (SBW) is a native pest in Minnesota that follows a "boom and bust" population cycle of about 30-40 years. During the 6-8 year "boom" phase, it devours new growth on balsam fir and white spruce trees. The “boom” phase persists until most food sources are depleted, leading to extensive tree loss. The outbreak of spruce budworm in Minnesota is expected to last until about 2029.

Spruce budworm eating on bow of spruce tree

SPRUCE BUDWORM LIFE CYCLE

Spruce Budworm LIFE CYCLE

Adult moths can travel up to 120 miles and lay hundreds of eggs in multiple locations. The eggs overwinter and emerge as larvae the following spring. The larvae prefer hot, dry summers, which is unfortunate, with regard to the changing precipitation caused by climate change.  During the 6-8 year "boom" phase, SBW larvae devour new growth on balsam fir and white spruce trees.  Since trees “prioritize” growth in their new branches, the loss of this investment is extremely harmful to the tree.

SPRUCE BUDWORM & FIRE

Wildfire in woods

The aftermath of SBW infestations also includes a heightened risk of wildfires. Dead trees left behind serve as fuel on the forest floor, increasing both the likelihood and intensity of fires.  Standing dead trees serve as "ladder fuel" that can ignite the canopy. In fact the SBW is considered a major contributor to the 2021 Greenwood Fire in Minnesota, which burned nearly 30,000 acres and closed the Boundary Waters Canoe Area Wilderness for the first time since the drought of 1976.

WHEN WILL SPRUCE BUDWORM END ?

Spruce Budwom Devistated trees

The “boom” phase of the SBW persists until most food sources are depleted and the population can no longer sustain itself, but not before leading to extensive tree loss. The previous SBW outbreak in Minnesota was in the 1980's, with a peak defoliation of about 440,000 acres in 1986.  In 2023, SBW defoliated about 665,000 acres in Minnesota. The current outbreak of spruce budworm is expected to last through approximately 2029.

SBW IMPACT & CLIMATE CHANGE

spruce trees dying from the spruce budworm

Climate change exacerbates the Spruce Budworm (SBW) problem, as the trees are already stressed from heat and drought, and with weakened defenses, trees are more susceptible to insect infestations such as the SBW.  Climate change is also expanding the geographical SBW range; warmer temperatures allow the SBW to persist in regions where they were less prevalent in the past.  Further, climate change extends the growing season, allowing the “boom” phase of the SBW lifecycle to last longer due to warmer temperatures. 

Emerald ash borer on large green leaf

The emerald ash borer (EAB), an invasive pest originating from Asia, is a severe threat to all ash tree species such as green ash, white ash, and black ash. With more than 1 billion ash trees in Minnesota, numerous areas in the state are particularly vulnerable to EAB infestations, amplifying their devastating impact.

Black Ash Minnesota forest

North central Minnesota is home to over 1 million acres of black ash wetlands that are specifically suited to this tree species.  This concentration of ash presents additional hurdles for forestry experts striving to contain EAB. Replanting these large areas with other species of trees is a significant challenge and will take the work of many individuals and organizations working together.

EMERALD ASH BORER IN MINNESOTA

EMERALD ASH BORER IS MOVING NORTH

Unfortunately, the northward movement of EAB threatens Minnesota's vast ash forests. While foresters initially hoped colder temperatures in northern Minnesota would deter EAB infestations, the spread of the pest has only been slowed down by the cold. Moreover, the warming winters attributed to climate change are expected to exacerbate the issue in the coming years, making EAB an increasingly serious threat to Minnesota's ash tree populations and necessitating proactive measures such as planting new tree species in these areas, to mitigate the impact of EAB on forest ecosystems.  While it is feasible to treat ash trees infested with EAB in a private yard or in the city, this is not feasible in the huge areas of ash in Northern Minnesota.

dying trees fron the emerald ash borer

The warming winters attributed to climate change are expected to exacerbate the issue in the coming years, making EAB an increasingly serious threat to Minnesota's ash tree populations and necessitating proactive measures such as planting new tree species in these areas, to mitigate the impact of EAB on forest ecosystems.

EMERALD ASH BORER LIFE CYCLE AND IMPACT

Transporting Firewood

EAB can only move up to a mile per year on its own from one site to another, but has been aided by people moving ash firewood from one place to another. 

Emarald ash borer damage to ash tree

It has a 1-2 year life cycle, and primarily lives underneath the bark, with the larvae creating tunnels or "galleries" that disrupt the tree's ability to transport water and nutrients.

Emerald ash borer d shaped exit holes

While ash trees can survive a light EAB invasion, a full infestation will lead to the death of the tree within 1-3 years of visible symptoms, such as the 1/8" “D” shaped exit holes.

1 Diverse Trees.jpeg
bottom of page