Love your oak tree? Don’t prune it right away or you could be putting it at risk for oak wilt

There are ways to help a damaged tree

Oak tree. (Michigan Department of Natural Resources)

Do you have an oak tree? You could save its life by putting your chainsaw down and not pruning it right away, according to the Michigan DNR.

Oak trees are at high risk for oak wilt infection between April 15 to July 15. Oak wilt is a fungal disease that can weaken white oaks and kill red oak trees within just a few weeks.

During this time of year, flying beetles can carry spores of the fungus from tree to tree. The fungus enters the tree through wounds that are often caused by pruning or storms.

“The guidelines against pruning oak trees during this time are designed to help prevent the spread of this tree-killing disease to new areas,” said James Wieferich, forest health specialist in the Michigan Department of Natural Resources’ Forest Resources Division. “Once oak wilt gets started, it is expensive to successfully manage and will kill all nearby red oaks over time, if untreated.”

How can you help a damaged tree?

Have you already pruned the oak tree? Was it damaged some other way? THere’s still time to help. If you have an oak tree that was damaged during the high-risk period you should cover all wounds with tree-wound paint or latex-based paint.

Painting tree wounds is not recommended for other tree species because it can reduce the effectiveness of the healing process, according to the DNR.

Oak wilt beetle. (Michigan Department of Natural Resources)

What is oak wilt? What are the symptoms?

Oak wilt was first discovered in the 1940s. It is widespread across Michigan.

Red oaks are most susceptible. Red oaks have leaves with pointed tips and include black oak, northern red oak, and northern pin oak. Trees in the white oak group have rounded leaf edges and include white oak, swamp white oak, and bur oak.

Symptoms usually appear from late June until September. Trees will wilt from the top-down, rapidly dropping leaves, which can be green, brown, or a combination of both colors.

The fungus can move through root grafts to oaks about 100 feet away. Untreated, oak wilt will continue to move from tree to tree. As more trees die, more fungal spores are produced, which allows the beetle to carry infection to new locations.

Don’t transport infected firewood

Firewood cut from an infected tree can still harbor fungus. Don’t move firewood from one place in Michigan to another.

If you suspect your firewood has oak wilt, you can help slow the spread by burning it, chipping it, or debarking it before April.

Once the firewood has been dried for longer than a year and/or all the bark loosens, the firewood will no longer spread oak wilt.

How to report oak wilt infections

The DNR restricts cutting of red oak trees on state land between April 15 and July 15. The DNR is urging private forest landowners to use caution and delay harvesting activity in oak forests until after July 15.

You can use this interactive map to report infections. If you need more information you can reach out to DNR-FRD-Forest-Health@michigan.gov.

Michigan State University’s Diagnostic Clinic also can verify oak wilt infection. Click here to view online instructions or call 517-355-4536.

Click here to learn more from an oak-wilt specialist. If you want to learn more about invasive species in Michigan, you can click here.


About the Author:

Kayla is a Web Producer for ClickOnDetroit. Before she joined the team in 2018 she worked at WILX in Lansing as a digital producer.