In 1944 the first outbreak of Oak Wilt was seen in the state of Wisconsin. Since then the deadly disease has killed oak trees in 25 states.

What Is Oak Wilt

Oak wilt is a disease caused by a fungus that can bring down an oak tree in short order. It can move between an infected tree and an uninfected tree both above ground and beneath ground. When it moves underground, it does so when the two trees graft together.  Generally speaking, grafts happen when the trees are the same species. But with oak trees, root graft happens even when the oak trees are of different species.

Then there’s this pesky beetle that eats the sap of an infected oak tree, makes it way to a healthy oak tree and tranfers the fungus to the clean oak.  The oak wilt fungus is most commonly spread by the beetle between April and July.

Symptoms of Oak Wilt Disease

If you have Oak trees on your property you’ll want to watch for symptoms of oak wilt disease. When a tree is infected, it wilts from the top down, a few branches at a time. The branches, when infected, have brown streaks in the wood just beneath the bark.  The tree’s leaves drop fast and they are usually brown, green or a combination of the two colors. In Red Oaks and Bur Oaks the leaves look wet and they curl around the midrib.  The Minnesota DNR describes what happens as oak wilt disease spreads. “An infection pocket is created with dead trees at the center and infected trees with  wilting crowns around the edges in a bull’s-eye pattern.”

Red Oaks, Black Oaks, Eastern Pin Oaks, Northern Pin Oaks and Scarlet Oaks often die 4-6 weeks after being infected by oak wilt. White Oaks, Swamp White Oaks, Bur Oaks generally live longer but they also succumb to the disease.

Once you see symptoms of Oak Wilt disease, your first call should be to a local tree care expert. They’ll likely need to have the tree removed. Best to do this rather than let the disease spread and kill all your trees.