Is there anything better than springtime in the north woods?

Walking wooded trails with the spring sun shining through miles of forest canopy around me is the favorite part of my job (especially before the bugs come out). Even just driving around, you see the pastel colors of baby leaves unfurling on every hillside. My oldest used to call it “Spring-Fall” because of the colors. This is also the favorite time of year of an invasive and lethal disease that is killing one of the northeast territory’s most abundant and valuable tree species: oak. The disease is oak wilt (bretziella fagecarum).

New oak wilt infections are easily started during the spring and early summer when, 1.) The oak wilt fungus pops their mushrooms (spores) under the dead bark of trees it killed last year, and, 2.) beetles feeding on the sweet-smelling spores are active.

This is known as high risk oak wilt infection season. Any fresh wound on an oak tree makes it vulnerable to infection. The risk of oak wilt continues mid-summer through fall, but biological conditions make the risk somewhat lower than spring-early summer. Red oaks infected by oak wilt die quickly, within six to eight weeks. Size, health, and quality of the trees doesn’t matter, the disease can affect a 40-foot, 200-year-old champion or a scrubby 10-year old in the sand plains.

Oak wilt spreads in two ways. Overland infections occur when native nitidulid beetles (and a few other types) feed on the apple cider-smelling spores, and then fly off to lap up sap on wounded oak trees, carrying the spores on their little bodies to the wound. Once an oak tree is infected, the oak wilt fungus moves through the tree into its root system and into all oak trees that it shares roots with. Oak roots are connected in a vast underground system of “root highways,” allowing oak wilt to move and kill acres of trees until the disease runs out of oak roots to move through. This below-ground activity across root grafts is responsible for the greatest number of trees killed by oak wilt. A tree’s roots can grow twice the distance that a tree is tall. So, for example, a 50-foot oak tree can have roots 100 feet out from its base in all directions.

All is not lost. This is different than the ash borer. Oak wilt can be prevented and, where detected, stopped. Prevention is key to managing the disease and limiting its devastation. Don’t injure oaks during the growing season (when leaves are on the trees). Rapidly seal wounds if they occur (spray paint). Beetles are strongly attracted to that fresh oak wood smell, and will arrive in minutes. Don’t move oak firewood unless it’s dry enough for the bark to be peeling off. Monitor for the disease and get a prompt identification. Diagnosis of oak wilt requires the presence of the pad of spores (mushroom), or a positive lab analysis.

While out enjoying our oak forests, if you notice something unusual — a change in leaf color, rapid leaf drop at the wrong time of year — contact a Michigan oak wilt specialist or your Conservation District to assist you with accurate diagnosis. Our oaks endure many native pests and diseases which can easily be confused with oak wilt symptoms. If oak wilt is diagnosed, successful treatment requires technical expertise.

Go to michiganoakwilt.org to connect with trained oak wilt specialists, learn about ongoing research in Michigan, and find helpful information and photos.

Eric Brandon lives in Harrisville and serves Alcona and Iosco counties as Conservation District forester.