Eastern spruce budworm

Quick facts

  • Spruce budworm activity has been observed in Minnesota every year since at least 1954.

  • Management strategies include commercially thinning healthy stands to retain trees with greater than 40% live crown ratio.

  • Using pesticides to control spruce budworm is expensive and not very successful at treating forests, but is an option for saving yard trees.

  • If dead and dying trees are not removed, they become a fire hazard around homes and buildings and contribute to increased fire risk.

Managing spruce budworm in Minnesota's forests

The eastern spruce budworm (Choristoneura fumiferana) is a native forest insect of concern across Minnesota’s coniferous forests. Spruce budworm is responsible for defoliating and/or killing vast acreages of balsam fir and spruce annually in Minnesota.

Despite its name, balsam fir trees are most susceptible to budworm while spruces are moderately susceptible. Fortunately, these important conifer species can be protected through effective forest management.

The impact of spruce budworm

Large-scale outbreaks of spruce budworm in the eastern Canadian provinces and northern New England typically occur cyclically every 30 to 40 years.

In Minnesota, budworm activity has been observed every year since at least 1954, representing an endemic budworm population for over 60 years. Budworm outbreaks in Minnesota typically occur in the same area every 25 to 40 years.

Estimates from the Department of Natural Resources suggest that annual budworm defoliation averaged 94,500 acres of Minnesota’s forests from 2010 through 2014.

Spruce budworm life cycle and symptoms

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Management strategies

Forest management actions can reduce losses from budworm damage.

If you start to notice budworm populations in stands of balsam fir, make plans to have them harvested as soon as possible to maintain their value. Don't wait to harvest trees.

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Matthew Russell, Extension forester; and Michael Albers, Minnesota Department of Natural Resources, retired

Reviewed in 2018

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