However indestructible they might look, even the mightiest trees can be felled by disease. One of the worst diseases that ravages trees in Minnesota is oak wilt, a fungal disease that afflicts all oak tree species found in the state. If an oak tree is infected with oak wilt, it will decline and eventually die unless treated promptly. To avoid losing these majestic trees to this terrible disease, it’s important to be able to recognize symptoms of oak wilt so that you can take action immediately.
Common Symptoms of Oak Wilt
While all oak species in Minnesota are vulnerable to oak wilt, it’s worth noting that some species are far more susceptible than others. In red oak species, including the northern red oak and northern pin oak, oak wilt will progress rapidly and the afflicted tree will die in just one to four months. In white oak species, such as the bur oak and swamp white oak, the disease progresses much slower, with tree death not occurring for two to five years after infestation.
The most noticeable symptom of oak wilt will be discoloration of the leaves. The leaves of an infested oak tree will turn brown around the edges and wilt until they drop. If you notice browning and fallen leaves on your oak tree in spring or summer, it’s likely fallen victim to oak wilt. In red oaks, leaf discoloration and wilting will begin in the crown of the tree before descending down the trunk. With white oaks, leaf wilting happens more slowly and will usually appear in just a few scattered branches at first before spreading over the years that follow.
Another symptom of oak wilt is cracking bark along the trunk and branches of the trees. When bark is peeled off, there will likely be a discoloration on the wood beneath that may be bluish, brownish or black depending on the species of oak tree. Mats of the fungus itself may also begin to grow on the trunk of the tree. If you cut off branches of an infested tree, you may also notice the fungal infection in the form of discolored rings within the wood.
How to Prevent Oak Wilt
While it is possible to treat infested trees for oak wilt, it’s more reliable and more cost-effective to take measures to prevent oak wilt from spreading to your property. Oak wilt is primarily spread by sap beetles that, as their name suggests, feed on the sap of trees. Sap beetles are often attracted to open wounds on infested oak trees, then transmit the oak wilt fungus to healthy trees. To minimize the risk of oak wilt transmission, avoid pruning your oak trees between April and June, when sap beetles are most active in Minnesota.
It’s also best to be wary of purchasing firewood from oaks. If oak firewood is infested with oak wilt, it may spread to oak trees on your property, either from traveling spores or sap beetles feeding off of it before moving to your trees. The other primary way in which oak wilt spreads is between the roots of oak trees. To avoid this, if an oak tree on your property is infested and past saving, schedule tree removal ASAP to get rid of it before the fungal disease spreads to nearby trees.
The best way to protect your oak trees from the scourge of oak wilt is by hiring a team of professional arborists to apply preventative treatments. Connect with Pro Tree today if you’re in need of oak wilt prevention services in the greater Twin Cities area!