REGIONAL— Defoliation from spruce budworm reached its highest level in Minnesota since 1995, last year.
According to the DNR, approximately 303,000 acres of balsam fir and spruce suffered defoliation, while about 81,000 acres of balsam and spruce were killed as a result of repeated defoliation and last year’s drought conditions.
Most of that damage occurred in Lake and western Cook counties.
Spruce budworm has defoliated or destroyed an average of 282,000 acres of fir and spruce forest per year in northeastern Minnesota since 2018. Despite its name, the spruce budworm prefers balsam fir but will also feed on other species, including spruce, tamarack, and pine, when populations are high.
Unlike other parts of the U.S. where the budworm essentially disappears after massive outbreaks, the budworm population in Minnesota has a continuing population that has been observed in the Arrowhead region since 1954.
In Minnesota, spruce budworm typically feeds in an area for six to eight years, which is about how long balsam fir can withstand defoliation before it dies. The population then moves to a different zone in northeast Minnesota.
The past few years of dry weather, particularly in the spring and early summer, may have worsened the spruce budworm situation. Scientists suspect that warm, dry weather increases the survival of budworm larvae.
Last year’s forest damage, combined with drought, possibly played a role in Minnesota’s fire season, including with the 27,000-acre Greenwood fire in Lake County, which burned in the heart of the budworm outbreak.