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What Are the Signs of Oak Wilt and How Is It Treated?


Oak trees are a very commanding type of tree, and when they stand strong and healthy, they add a certain majesty to a yard or property. However, should the tree be sick and showing signs of oak wilt, you’ll notice a change in appearance and presence of the tree. Signs of oat wilt on leaves are relatively easy to see, but understanding how to identify it, why it happens, and how to treat it means taking a closer look at the tree and calling in the professionals to assist.

What Oak Wilt Looks Like

Since oak wilt starts atop the crown of the tree, it might not always be possible to see what’s going on with the naked eye. Using binoculars for taller trees, take a look at the leaves on top and identify their color. Oak wilt usually occurs in the late spring to early summer, and it starts with a rapid browning of the leaves. Then they start to fall off the branches. Looking at the individual leaf, the wilt will appear at the tip of the leaf and move inward, down the margins, and to the stem.


Oak wilt doesn’t just present in the leaves of the tree, but it can also be detected in the bark. Another symptom of the disease is vertical cracking of the bark, and fungal spores will be visible underneath. The bark may eventually burst and peel back, allowing sap beetles to better access the fungus and consume it. It might seem like this is a natural solution to “removing” the fungus, but what actually happens is that the beetles “pick up” the fungal spores and transfer the disease to other trees.

Oak wilt can present with the following symptoms:

  • Discoloration of the leaves
  • Dying or dead crowns
  • Unhealthy or dying appearance of the tree
  • Leaves are curling or wilted
  • By the middle of summer, the leaves have completely fallen off the tree

Red oaks (black oak, northern red oak, pin oak, etc.) are more susceptible than white oaks (bur oak, white oak, swamp white oak, etc.). Because their roots tend to graft with other roots around them, red oaks get sicker. They will usually fall to the fungus and die within a few weeks, whereas white oaks can hold out a bit longer, sometimes as long as a year after getting sick.

How Oak Wilt Spreads


As mentioned above, sap beetles spread the fungal spores and infect other trees and plants, but that isn’t the only way that oak wilt gets into a tree. Sap beetles will seek out the sweet-smelling sap when bark is broken. Bark can be damaged in various ways, including accidental cuts from pruning or damages from winds and storms. When the beetles eat from infected trees and then move to a healthy yet wounded tree, the tissue of the healthy tree gets infected, and then the tree tries to heal itself.

Just like humans, trees have evolved to heal superficial wounds themselves, but what they do to try to expel the fungal disease is to “cauterize” the wound, by “walling off” its cells. In turn, this causes the leaves to wilt, transition to brown, and fall from the tree. This wilting and browning response ultimately kills the branches and, left untreated, kills the whole tree. Oak wilt is a disease that moves quickly and can kill the tree in a relatively short time, often as short as a few weeks.

Tree Roots

Another way that a tree can get infected is through the grafting of roots underneath the soil. That is, when an infected tree’s roots “intercept” and grow together with the roots of a healthy tree, the disease can be transmitted further. Because oak wilt is a fungal disease, the spores can rapidly invade the root space of a healthy tree and make it sick. It can be incredibly hard to curb the spread of the disease once it’s in a neighborhood because the beetles can move from yard to yard, and diseased roots won’t care if there’s a fence built in between houses. The spores will keep infecting regardless.


Even spores that are carried on the wind and land in open wounds of newly pruned trees can quickly infect the healthy tree. It is imperative to treat oak wilt as soon as it is identified so as to protect neighboring trees.

Oak Wilt Treatment

Unfortunately, once infected, there is no way to save the tree. The only course of action with regard to oak wilt is prevention. Be aware of damages to an oak tree and get them patched up and protected immediately. Sap beetles can move quickly and can find an open wound on a tree and be eating there within a mere half-hour.

Additionally, do not prune at any time between April and August. It’s important to stay vigilant when mowing the grass or doing anything around the tree (such as using power tools) that could damage the roots or bark.

Another mode of prevention includes being cautious about firewood. If you’re not sure where it came from, don’t transport it around or near any oak trees. There is still a possibility that the fungus can transfer from the fresh firewood. It’s best to store the firewood away from the oak trees, and the trees will be best protected by keeping the firewood under a tarp. Cover the firewood tightly and securely so as to really keep it dry. The dry wood will starve out any remaining fungus, and because there is nothing you can do once the tree is infected, it really is better to be safe than sorry.

If you’re not sure as to whether your tree is infected by oak wilt, don’t waste any time and give our professionals at Vernon Imel Tree Services a call. We can help diagnose oak wilt and set a course of action.