Eastern spruce budworm is a native caterpillar and is the most destructive pest of spruce-fir forests in eastern North America. Caterpillars prefer to feed on balsam fir and white spruce needles, but minor feeding damage can occur on black spruce, tamarack, and various pines.
While the northeastern United States and southeastern Canada experience major outbreaks every 30-40 years, some visible defoliation in most years has occurred in northeastern Minnesota since at least 1954 when annual monitoring began. In Minnesota, outbreaks last about eight years before moving to a new area, and 30 to 40 years pass until spruce budworm returns. The majority of the current outbreak of spruce budworm is in northern St. Louis, Lake, and Cook counties. Outbreak conditions eventually lead to widespread balsam fir and white spruce death. This tree mortality is also a concern for wildfire activity as it creates fuels which can contribute to the spread and intensity of fires.
Location
Eastern spruce budworm is found throughout northern and central Minnesota, wherever spruce and fir are present.
Learn more
Watch this webinar about Eastern spruce budworm’s impact on Minnesota, presented by a DNR forest health specialist.
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The movement of spruce budworm in northeast Minnesota displayed above from 1998-2025. Outbreak centers and years are displayed in addition to major wildifires that occurred in 2021 and 2025.