District Forester Eric Brandon gives a presentation on oak tree wilt for the AuSable Valley Audubon Society.

OSCODA – District Forester Eric Brandon paid a visit to the January AuSable Valley Audubon  (AVA) meeting to educate locals about oak tree wilt.

According to the Michigan Oak Wilt Coalition, oak wilt is defined as an exotic, invasive and lethal disease of oak trees. It’s caused by a fungus called Bretziella fagacearum which clogs the water conducting vessels of the infected tree and causes them to wilt and die.

According to Brandon; however, oak tree wilt hasn’t always been an issue or a concern in Northern Michigan. He explained the first sightings of oak tree wilt started in Wisconsin in 1881. From the 1970s to now, oak wilt has spread immensely and has impacted lake states and Texas. More specifically, over the last few years Brandon has seen oak wilt around the area.

Throughout the presentation, Brandon touched on the history of oak wilt, how to spot it, when to be pruning and not pruning your trees as well as the hazards associated with oak wilt.

According to Brandon, red oaks and white oaks are most commonly infected. When a red oak is infected it is considered a deadly kill meaning the disease will kill the tree quickly. Typically, leaves appear with red patches on the ends and are needle point sharp. A white oak typically experiences a slow kill when infected with oak tree wilt. 

One of the first symptoms local residents should look for when searching for oak tree wilt is in June to August, if the top of the tree has leaves that have been discolored to a dull olive green. According to the coalition, that is one of the first signs that the tree has been infected. Other oak wilt symptoms include bark cracks and fungal mats.

After that, the discolored leaves will wilt from the top of the tree downward and become brown and bronzed. Quickly following the leaves will drop rapidly as the disease progresses. Within a few weeks all the leaves will have fallen off.

According to AVA members, the oak tree is home to 534 species of butterfly and moss, so making sure they continue to survive is important. Further, the total value of a standing red oak timber is estimated at more than $1.6 billion, according to the Michigan Department of Natural Resources.

Although oak tree wilt is an issue, Brandon stressed that its the spreading of the infection that’s caused it to be in our own backyard. According to Brandon, the infection is spread from nitidulid beetles who carry spores from infected trees to an injured or freshly pruned tree.

The fungus can also move without the help of the beetle. The fungus on an infected tree can actually injure nearby trees that are connected through their root systems, better known as root grafts.

The best way to prevent an oak tree from being infected with oak wilt is to prune trees at specific and safe times of year. According to Brandon, the safest period for residents to trim their trees is Nov. 1 through March 14, during this time the infection is dormant, so its incredibly difficult for the tree to develop the infection.

According to the coalition, if pruning is necessary at any other time of year, residents are encouraged to cover all oak tree wounds with tree wound paint or latex paint. The most risky time of year to prune an oak tree is between April 15 and July 15, according to Brandon.

If you believe you have an infected oak wilt tree, contact an oak wilt qualified specialist at