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Oak wilt in Minnesota

Quick facts

  • Oak wilt is a fatal tree disease caused by a fungus that affects all species of oak trees. 
  • Oak wilt spreads from diseased to healthy trees either below ground via connected roots or above ground by insects.
  • DO NOT prune oaks from April through July to prevent infection by sap beetles. Immediately cover unavoidable wounds with a latex-based paint or shellac.
  • DO NOT move logs or firewood from recently wilted oaks, and don’t move fresh oak firewood from oak wilt-infected areas.
A white oak tree.

Current oak wilt risk status in the Twin Cities - LOW

Depending on weather conditions and insect populations, infections could occur but would be rare. Immediately treat pruning wounds, stump surfaces and other wounds.

In general for Minnesota, the risk level is low from August through October. Risk level can vary considerably based on seasonal change and location. Always check the oak wilt risk status for your date and location before pruning or wounding oaks.

Oak wilt range and symptoms

Oak wilt is caused by the fungus Bretziella fagacearum and is responsible for killing large numbers of oaks every year in Minnesota.

Oak wilt is most severe in the red oak species group such as northern red oak (Quercus rubra) and northern pin oak (Quercus ellipsoidalis). It also affects white oak (Quercus alba) and bur oak (Quercus macrocarpa), but it kills them more slowly.

Fortunately, several management techniques exist to prevent or control oak wilt.


Oak wilt prevention and control

The coordinated use of several actions is the best strategy to stop the spread of the oak wilt fungus. An integrated management approach for a property with oak wilt could involve:

  • Root cutting.
  • Treating uninfected, high-value trees with fungicides.
  • Removing wilted red oaks that continue to produce the oak wilt disease.
  • Properly disposing of logs from wilted trees.

Authors: Jennifer Juzwik, research plant pathologist, U.S. Forest Service; Brian Schwingle, forest health specialist, Minnesota DNR; and Matthew Russell, forester

Reviewed in 2023

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