All species of Oak can become infected with this disease, however, it is more common in Red Oak subgenus species, such as Black, Red, Scarlet, Hills, and Pin. This is in contrast to White Oak subgenus species, including White, Swamp White, Bur, English, and Chinquapin.
Red Oak species can die or decline rapidly after coming down with Oak Wilt, usually within weeks or months, while White Oak species generally experience a slower decline. But not all infected trees die; some species of White Oak have been known to spring back after one year or so.
Causes and Symptoms
Oak wilt is mostly spread through transmission of root graphs. Sometimes, when trees are within 50 feet of one another, their underground root systems will actually fuse together and share the same vascular system. This network of tree roots allows the Oak Wilt fungus to transmit freely among trees. This is why it is common to see an entire string of infected trees. Oak Wilt can also be spread through beetles carrying fungal spores from tree to tree.
The fungus, Ceratocystis fagacearum, invades the Xylem (tissues or vessels that conduct water dispersal in trees), which prompts a tree to essentially clog its own water distribution system. This, of course, inhibits the normal rate of water flow from the roots to the canopy of the tree, resulting in a wide range of symptoms and after-effects. The most distinguishable effect is wilting leaves and foliage, hence the name “Oak Wilt.”
Common Symptoms in Red Oaks
Oak Wilt in Red Oak subgenus species usually begins at the tree’s canopy, and simultaneously works its way downward and inward throughout the tree. This is made evident by leaf discoloration (grayish-green or brown tips), complete defoliation, weakened bark, fungal mats and patches, fruity odor, sticky sap-like fluid production, insect infestation (namely picnic beetles and bark beetles), and more.
Common Symptoms in White Oaks
Common symptoms of Oak Wilt in White Oaks are nearly the same as the symptoms seen in Red Oak subgenus species. The only difference is the time-frame in which the symptoms appear and last. White Oaks experience symptoms slower, usually between 1 and 6 years, and also more localized on the tree, such as its branches. And they do not lose all their leaves.
Cures and Control
There is still no way to really cure an infected Oak Tree. Some have found that fertilizer tree injections directly into the root system can be an effective form of treatment. But often times, tree removal is the best option. Prevention is the most effective way to prevent your Oak Trees from becoming infected with Oak Wilt and other diseases. Professional, routine tree care is a viral part of protecting your landscaping trees, as well as, proper pruning, mulching, watering, and fertilizing. Talk to your local tree service specialist for professional advice regarding proper tree care.