Strength. Beauty. Longevity. These are the types of positive attributes often used to describe oak trees. Yet, like other trees, the unique qualities of oaks are paired with unique susceptibilities — an example of which is oak wilt.
Oak wilt (or Bretziella fagacearum) is a fungal disease that infects the vascular system of oak trees, and — as the name suggests — causes leaves to wilt, become discolored, and eventually die.
Oak wilt transmission happens in one of three ways:
Among the oak species, red oak trees are most susceptible to oak wilt, often dying within 1-2 months of being infected. Red oaks are often the site of fungal spores, and their symptoms are not always as apparent.
Arborists first discovered oak wilt in Wisconsin in 1944 and declared it a harmful disease. As of 7-3-24, there are confirmed oak wilt cases in over 50 Michigan counties per Michigan Department of Natural Resources.
Oak Wilt Mapper from MI Department of Natural Resources, 7-3-24; Red Dot = Confirmed Oak Wilt Case
With the majority of red oaks unable to recover from oak wilt, the need for proactive measures is clear. Here are some simple yet effective ways to prevent the spread of this damaging disease.
Trimming away weak or dead branches from trees — otherwise known as pruning — is one of the most effective ways to keep them strong and healthy. Like other trees, only prune oak trees during the winter months. Not only is it easier to identify branch patterns during this time, but there is also less insect activity and subsequent infections to worry about.
In the case of sap beetles, these insects are most likely present between mid-April and mid-July. (Note that some types of beetles can be active during the summer and into the early fall.) Avoid pruning during these because the risk for infection is highest
Avoid moving firewood many miles from its original location, whether it’s to a vacation property or a campsite. With this transport comes an assumed risk that the firewood may carry a disease that can harm subsequent trees.
If you’re cutting a tree infected with oak wilt to use for firewood, make sure it remains in one area to avoid transmission to healthy trees. And throw a tarp with no holes over the wood to cover it. This will keep beetles from feeding on the sap of the wood and picking up fungal spores.
At Safari Tree, we recognize that trees have unique needs and face unique threats. That’s why we’ve developed a comprehensive tree health care program that ensures trees can effectively resist and recover from any number of health issues (oak wilt included).
If you’re a Michigan homeowner in need of tree care, we encourage you to reach out to the Safari Tree team and request a FREE quote.