The Michigan Oak Wilt Crisis


Originally published December 2014

Oak Wilt has been on the rise in Michigan and recently there has been such a spike that it has become an epidemic, especially on the west side of the state. It has spread across the state so anyone that has oak trees here should be aware and be monitoring for infection. The decimated numbers of oak trees in urban forests are bringing about a dramatic change in the area’s ecology, resulting in decreased air quality and hazardous clusters of standing dead trees. Arborjet’s Joe Aiken, the Great Lake’s Regional Technical Manager, filled us in on the current crisis in Michigan.

Oak Wilt Awareness

“A few emails have gone out, geared toward the forestry industry, but information hasn’t been targeted to the general public. I really want to get more information out to homeowners. One group in particular that I am concerned about are vacation cottage owners in Northern Michigan that may not be aware of the situation because they are not there enough. If you or a neighbor have a red oak in your landscape, you want to monitor oak wilt because if they have it, the fungus can spread rapidly through root grafts” explains Aiken.

Don’t Move Firewood

The Michigan Department of Natural Resources released a bulletin on December 1, 2014 advising against the movement of firewood between state parks to help prevent the spread of oak wilt. Michigan DNR Parks and Recreation has been working the last several years to stop the spread of oak wilt at state parks.

Proper Pruning

According to Aiken, “One important thing for the people of Michigan to understand is when to have an oak tree pruned. The fungus colonizes in the wound of the tree so when it is warm out you shouldn’t be cutting oak trees. The fungus is easily transported by beetles from infected wood to nearby wounded trees.”


Oak wilt is a lethal tree infection that cannot be cured and causes rapid death of untreated trees. Once the Red Oak trees become infected they can die anywhere within a month to a year. “People are shocked to be losing their oak trees faster than they lost their ash trees to Emerald Ash Borer. With the red oak it is that fast and that is why it is so important for people in Michigan to be aware of the signs and symptoms.”

Basic Identification

Initial symptoms of oak wilt are browning leaves, beginning at the leaf tip and moving downward toward the stem. As the disease progresses, limbs will die off. Fungal mats may develop under the bark, pushing the bark outwards causing deterioration.

Oak Wilt is a disease caused by an oak specific fungus (Ceratocystis fagacearum) that spreads through root grafts and by insects. The infection causes leaf discoloration, defoliation and death.

Red Oaks are particularly susceptible to Oak Wilt and often succumb quickly. White oaks are more tolerant of the infection as they do not form damaging fungal mats.

Be Pro-active & Get Information

Would you like to learn more about Oak Wilt? If you have any questions about diagnosis contact a certified arborist for an evaluation.