Step aside beech bark disease, there’s a new cowboy in town! Who is this cowboy? Beech leaf disease, or Litylenchus crenatae ssp. mccannii. This disease is found in both our native American beech and ornamental European beech and is most easily recognized by the dark bands on the leaves. What’s causing this disease? Researchers have found nematodes (microscopic worms) overwintering in the leaf buds but are not sure yet if it is the cause of the disease or if it is just a carrier. Researchers are not sure of its origin but found a closely related subspecies in Japan.
It was first found in Ohio in 2012, and the first confirmed case in Michigan was in St. Clair County in 2022. The disease may be spread by wind and by animals, and humans transporting infected materials. While there is no official treatment yet, there are trials being conducted in Michigan that were found to have been successful in Ohio.
When looking for symptoms, the lower branches are likely to be infected first before higher branches. Because all the damage happens during the winter, you will not notice any worsening symptoms during the growing season.
Beech leaf disease has three stages of symptoms. The earliest symptoms are dark bands of thickened tissue on the leaves in between veins, as captured in the photo above. The second stage is characterized by puckering between leaf veins and distorted leaf shape. In the third stage, the leaf never emerges from its bud after winter (called “aborted buds”). After 6-10 years of disease progression, tree death is highly likely. Saplings are more likely to be affected and have a higher mortality rate than older trees. Beech leaf disease can potentially be confused with Beech leaf curl aphid, beech erineum patch, anthracnose, and powdery mildew.
Friends of the St. Clair River is helping Lake St. Clair Cooperative Invasive Species Management Area
(CISMA) survey stands of beech trees for this disease to determine the extent of its spread. How can you help? If you know of a place where there are beech trees in St. Clair or Macomb Counties, please let us know with our beech tree report form. If you have found beech leaf disease anywhere in Michigan, please use Midwest Invasive Species Information Network (MISIN)’s report tool to report it. Thisis especially important for new sightings and reportings.
Skyler Principe is a Program Assistant with Friends of the St. Clair River, where he monitors St. Clair County’s beech trees for beech leaf disease on public and private properties.