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Spruce budworm infestation impacting Lake States timber

State resource agencies are alerting owners to be aware

Photo from University of Minnesota Extension

MADISON, Wis. -- State forestry organizations in both Minnesota and Wisconsin are reporting that the effects of spruce budworm in northern forests is leading to severe defoliation in balsam fir and white spruce. Defoliation over a period of years can cause tree disease or mortality.

Spruce budworm infestations can last for 10 years. The Wisconsin DNR estimates that the current outbreak began in 2012.

The Michigan DNR has not reported an outbreak, but the Wisconsin outbreak likely is impacting the Upper Peninsula since all of the Northern Wisconsin counties that border Michigan have reported outbreaks.

The University of Minnesota Extension reported that this invasive species (which is native to North America) returns every 25-40 years. The infestation takes the form of budworm larvae in May and June that emerge as moths in July.

Tree damage will eventually take the form of reddish brown needles in the crown of spruce and fir trees. Spreading can be prevented by early use of commercial thinning after the larvae are first detected. Continued defoliation from the disease can result in top kill in two to three years in balsam fir and three to five years in spruce.

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