Forest Health_Content Page_Annual Reports

Forest Health Annual Reports

The DNR forest health team works to prevent, detect and control Wisconsin's forest pests, particularly invasive plants, insects and diseases that jeopardize trees and ecosystems. Through research, forest management guidance and education and outreach efforts, forest stability and sustainability is established and enriched.

Each year, staff create an annual report to give updates on the program and forest health threats in Wisconsin. Browse the newest reports below.

2025 Annual Report

Read about all of the latest forest health issues in Wisconsin, including:

  • The spongy moth outbreak, which peaked in 2023, collapsed in summer 2024. No defoliation was observed in 2025; however, moderate to severe oak mortality is now occurring in many areas that experienced severe defoliation during the outbreak.
  • State agencies such as DNR and the Wisconsin Department of Agriculture, Trade and Consumer Protection are working on a strategy to control the invasive pest hemlock woolly adelgid, which has not yet become established in Wisconsin but is moving westward and has reached the western lakeshore of Michigan.
  • Work continues to focus on biological control of emerald ash borer to aid in the protection of ash regeneration.
  • Beech bark disease was confirmed at a site in northern Menominee County, making it the second Wisconsin county (Door County was the first) in which the disease is known to occur. The insect beech scale, a contributing factor in beech bark disease, was found in several new locations in four northeastern Wisconsin counties, bringing the total to 13.
  • Invasive Japanese stiltgrass, previously only known in La Crosse County in Wisconsin, was discovered in four new counties in 2025: Rock, Walworth, Dane and Grant.

Read the Report

Annual report cover

Past annual reports

To access archived regional and annual reports dating back to 1951, contact your regional forest health specialist.