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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.
  • Oak wilt affects only oaks. It does not infect other tree species.
  • To manage oak wilt:
    • DO NOT  prune oaks from April through July to prevent spread by sap beetles. 
    • Stop below-ground spread by cutting root connections.
    • Don't move fresh oak firewood from oak wilt infected areas. Wait a few years after tree death before moving oak firewood.
    • Contact a qualified tree care professional regarding the treatment of high-value trees and if you want to cut root connections.

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 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 stop oak wilt.

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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.

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 continue to produce the oak wilt disease.
  • Properly disposing of logs from wilted trees.
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Authors: Jennifer Juzwik, research plant pathologist, US Forest Service; Brian Schwingle, forest health specialist, Minnesota DNR; and Matthew Russell, Extension forester

Reviewed in 2022

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