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Posted on: May 20, 2019

How to Protect Against Oak Wilt

red oak

Oak Wilt: How to Identify, Prevent and Control


What is Oak Wilt? 

Oak wilt is a deadly fungal pathogen disease that has spread throughout much of the oak range in Michigan and across the eastern United States.  Oak Wilt has the potential to impact the 149 million red oak trees across the forested land in Michigan.

Symptoms of Oak Wilt

An infected tree is often first noticed due to a sudden drop or browning of leaves in the summer months.  Leaves tend to brown from the tip to the stem.  Often the leaf tips and edges will be brown while the leaf base will remain green.  Oak death from oak wilt occurs rapidly, beginning at the top of tree and proceeding downward. Complete leaf loss and tree death can happen within two to three weeks.

How is it Spread?

Root System 

Spread of oak wilt occurs when the fungus travels through the roots of infected and healthy trees.  Once a single tree is infected, the disease will spread to other oaks through their grafted root network.

Tree Trimming Tree Wounds

Oak tree trimming, pruning and harvesting during the warmer months, April – July, can result in more new tree infections. 

Insects

It is this time of year when certain sap-feeding beetles have the potential to spread oak wilt spores overland from oak to oak.

Firewood

Moving firewood from symptomatic oaks is one of the most common ways oak wilt is spread to new areas. Oaks that die this year will be especially hazardous next year.


Treatment and Removal 

Should injury to oak trees occur, tree wounds should be immediately coated with a latex-based paint. This is one of the few cases where tree paint is recommended.

Infected areas and oak wilt symptomatic trees require special disposal care and tree stump removal and treatment by certified arborists.  Trees already infected with oak wilt cannot be saved.

 

Prevention

Do not prune, harvest or thin oak trees during the warmer months, April – July.

  • Simply cutting the dead and dying oaks will not stop oak wilt. Trees can be protected with a fungistat chemical that prevents spores from germinating. This treatment needs to be done by a certified pesticide applicator and must be applied every two years.
  • Trench or plow in dense oak tree forested areas to disrupt the root grafts.
  • Do not move firewood.  If an oak tree is cut down, either chip, debark, burn or bury it. 
  • If you suspect oak wilt is active on your property, contact an arborist or a consulting forester.
  • Report suspect oak wilt in Michigan: Department of Natural Resources Forest Health Division: DNR-FRD-Forest-Health@michigan.gov or by phone at 517-284-5895.

oak wilt tree

Spore mat on tree with oak wilt, feeding ground for beetles

oak wilt leaves

Red Oak leaves with oak wilt


Resources:              MSU Extension Publication “Understanding Oak Wilt” May 7, 2018

                                MSU Extension Publication “Worried About Oak Wilt” April 5, 2019

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