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Environment & Climate Change

Don't prune your oak right now; you could kill it

OakWilt2_507964_7.jpg
Joseph O'Brien
/
USDA Forest Service

The Department of Natural Resources is warning landowners about a tree-killer that pops up this time of year. It’s called oak wilt. If you have oak trees you can help prevent the spread of the fungus.

“What we're really urging people not to do is to prune oak trees between now and July 15th. Our best science tells us that that is the time that wilt, which is a fungus, is most transferrable to trees,” explained Joanne Foreman, the Invasive Species Communications Coordinator for the DNR.

Beetles are drawn to the wounds from pruning the tree and they spread the oak wilt fungus

“Red Oaks are more susceptible to oak wilt than white oaks. You can tell the difference because Red Oaks have pointy leaf ends where White Oaks have rounded leaf,” Foreman said

Trees die within weeks of being infected. 

“If your tree is accidentally wounded, that you can try to do your best to save it by painting the wound with latex paint,” Foreman said.

If leaves in the center of the tree start to die or fall off, it’s time to call an arborist. You probably won’t save the tree, but an expert could help prevent oak wilt from spreading to other trees. The DNR says the fungus can move from an infected oak to neighboring oaks through root grafts. Roots of large trees can reach 100 or more feet.

The U.S. Forest Service says the roots must be severed, which is usually done using a trencher that can go deep enough.

Left untreated, oak wilt will continue to move from tree to tree, killing more red oak over an increasingly larger area according to a statement by the DNR.

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