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Oak wilt in Minnesota

Quick facts

  • Oak wilt covers a large area in Minnesota and affects all species of oak trees. Check the DNR website for an up-to-date oak wilt disease map.
  • To manage oak wilt 
    • Don't prune oaks from April through July to prevent spread by insects.
    • Stop below-ground spread by cutting root connections.
    • Don't move firewood from oak wilt infected areas.
    • Use fungicides on high-value trees.

Current oak wilt risk status — SAFE

Green acorn with brown, ridged top hanging from a gray branch with green leaves in the background.

November through March

During the Safe period, oak trees can be pruned without risk to the tree. There is virtually no risk that an oak can become infected with oak wilt by over-land transmission of the fungus.

Oak wilt range and symptoms

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

Oak wilt is most severe in red oak group species such as northern red oak and northern pin oak. Fortunately, this valuable resource can be protected by utilizing effective management techniques.

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Oak wilt prevention and control

The coordinated use of several actions is the best strategy to stop the spread of the oak wilt fungus.

You should get an accurate diagnosis of the disease before taking any control action. Hire an experienced tree care professional or consult the University of Minnesota's Plant Disease Clinic.

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 are potential oak wilt mat producers.
  • Properly disposing of logs from wilted trees.
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Jennifer Juzwik, research plant pathologist, US Forest Service; Brian Schwingle, forest health specialist, Minnesota DNR; and Matthew Russell, Extension forester

Reviewed in 2020

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