Oak Wilt Information

Oak Wilt is the most deadly disease facing oaks in Wisconsin today. Caused by a fungus, it almost always kills infected trees. Dead oaks can create hazards, reduce property values and aesthetics, and reduce wildlife habitat and water quality.

First detected in Sawyer County in 2012, Oak Wilt cases have increased significantly since 2016, including confirmed cases in the Town of Spider Lake.

Oak Wilt moves easily from tree to tree through the root systems and insects, making control costly and difficult. Prevention is the best approach.

Prevent The Spread
  1. Don’t prune, wound, or cut down oak trees from April through July. If oak are cut or injured, apply a pruning paint (latex paint also works) to the stump or wound surface ASAP, but not more than 48 hours later.
  2. Keep firewood local and know if the wood may be diseased. Do not transport firewood long distances to your property.
  3. Become familiar with Oak Wilt symptoms and contact your local DNR or county forestry office for help with diagnosis.
Know The Symptoms
  • Rapid leaf drop in late June through September. Generally starts at the top and outside of the crown and moves down the tree and inward.
  • Fallen leaves with a brown or bronze colored edge and green center or base.
  • Groups of dead oaks indicating root system spread of the disease.
For More Information

Contact Paul Cigan, Wisconsin DNR Forest Health Specialist for the Northwest region for more information on Oak Wilt diagnosis, prevention, and control.

Phone: 715-416-4920
Email: [email protected]