Summary includes findings on insect outbreaks, diseases and other impacts to Minnesota forests
The Minnesota Department of Natural Resources has released its 2025 Forest Health Annual Report which uses data from aerial surveys and on-the-ground site visits. The report compiles information about insect outbreaks, disease epidemics, and other impacts to the state’s forests.
The DNR aerially surveyed 13.5 million acres of Minnesota for damage to forests in 2025. Since the early 1950s, aerial surveys have been a valuable tool for discovering, tracking, and managing forest health threats like spruce budworm, oak wilt, storm damage, eastern larch beetle and more.
“By tracking the changes and trends of what’s impacting trees, the DNR provides information that landowners and forest managers can ultimately use to help make our forests healthier and more resilient,” DNR Forestry Division Forest Health Consultant Brian Schwingle said.
Key findings in the 2025 report include:
- Forests received enough precipitation in the 2025 growing season to limit decline in species like oak, aspen and birch. Appropriate precipitation levels increase trees’ resiliency to other stressors like pests and disease.
- No new counties have confirmed cases of oak wilt. The number of Minnesota counties with known oak wilt remains at 33.
- Surveys discovered emerald ash borer in six additional counties, increasing the number with known EAB infestation to 59 of the state’s 87 counties.
- Prior spruce budworm damage in northeast Minnesota fueled two large wildfires in May, which burned around 28,000 acres in total.
- The June derecho damaged at least 11,600 acres of forest in the Bemidji area.
Managing forests so they can thrive is a cooperative effort. Minnesotans can help keep trees and forests healthy through proper yard tree care and forest management.
To help reduce the spread of harmful pests and diseases, buy and burn local firewood and report oak wilt beyond areas where it is common. Report pests and diseases regulated by the Minnesota Department of Agriculture on the MDA website.