Eastern spruce budworm

The eastern spruce budworm is a native moth that has lived in the spruce-fir forests of North America for many centuries. In the North Central Region, this insect can be found wherever balsam fir and white spruce grow. It has been especially important as a forest pest in the northernmost counties of Minnesota and Wisconsin and in the Upper Peninsula of Michigan. Major outbreaks of the spruce budworm occurred in the Lake States during the 1960's and 1970's, but populations declined in the early 1980's. Spruce budworm populations fluctuate a great deal. The data below shows defoliation in spruce-fir stands for the last 43 years in Minnesota:

Impact of the spruce budworm on the forest depends on both the intensity and duration of the insect outbreak. The seriousness of the impact is also affected by the intended uses of the forest area where the outbreak occurs. Defoliation by the spruce budworm can result in growth loss, dieback of tree tops, and mortality of individual trees or whole stands of trees.

Management activities for the spruce budworm in the North Central Region include monitoring trends in spruce budworm populations, salvaging dying and dead trees before the wood becomes unusable, and decreasing the vulnerability of spruce-fir stands to this insect by using cuffing techniques that enhance diversity of tree ages, structural diversity of the forest, and encourage plant species not susceptible to spruce budworm.