Invasive beech leaf disease was first confirmed in Michigan in July 2022 after landowners noticed its distinctive thickened leaf bands on trees in a small wooded area in St. Clair County. Since then, new discoveries in Oakland and Wayne counties indicate the disease is more widespread.
Beech leaf disease is associated with the nematode Litylenchus crenatae, a microscopic worm that invades and spends the winter in leaf buds, damaging leaf tissue in American, European, and Asian beech species. Trees weakened by leaf damage become susceptible to other diseases and can die within six to 10 years of the first symptoms.
Affected trees have been found on properties in Birmingham, Bloomfield, China, Clay, Grosse Pointe Shores, Rochester and Troy. The condition of the leaves in these locations suggests that the infestation has been present for at least a year, possibly longer.
Though the leaves are changing and beginning to fall, Simeon Wright, a forest health specialist with the Michigan Department of Natural Resources, says there’s still time to check beeches for signs of the disease.
“We have now seen beech leaf disease in both patches and individual urban trees in southeastern Michigan. The disease causes dark, thick bands between leaf veins that can be seen on both green and brown leaves,” Wright said. “If you have beeches, take the time now to check for symptoms.”
Beech leaf disease nematodes are also associated with damaged leaf tissue and dead buds. Leaf curling and skewing can progress from one year to the next, resulting in wilted or yellow leaves and a thin canopy. Severely infested trees may lose their leaves in early summer.
Many questions about beech leaf disease are still unanswered. Researchers are still working to understand whether the nematode Litylenchus crenatae is the main cause of the disease or the carrier of another pathogen responsible for the disease.
“As a result, we don’t yet know all the avenues that the disease could spread,” Wright said. “Currently, no treatments are known to protect trees or reduce the impact of disease, although studies are ongoing.”
Michigan is home to approximately 37 million American beeches. The potential spread of this disease in the region could have a devastating impact on beech trees, which play a significant role in both forests and urban landscapes across the state.
Report possible infestation
Take the time now to look for signs of the disease on American or ornamental beech trees. If you suspect you have found a symptomatic tree, take one or more photographs of the infested tree, including close-ups of the infested leaves; note the place, date and time; and report it in one of the following ways:
Avoid moving beech material
First identified in Ohio in 2012, beech leaf disease has now been documented in areas of Connecticut, Massachusetts, Maine, Michigan, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Virginia and Ontario.
The microscopic nematodes cannot travel great distances on their own. It is possible for the disease to spread through the transport of infested nursery stock and other beech material containing leaves and buds. As a precaution, beech, tree material and firewood should not be brought from areas with known infestations.
what is done
Beech leaf disease was added to Michigan’s invasive species watch list in January 2021 to encourage nurseries, foresters, residents, and land managers to check for and report a suspected infestation.
Tree surveys continue statewide, with Michigan State University forest health researchers reporting no further evidence of beech leaf disease in their surveys this year. Researchers from the University of Michigan’s School for Environment and Sustainability are planning surveys for 2023, and the DNR and Michigan Department of Agriculture and Rural Development are working with cooperative invasive species management areas in southeastern Michigan to expand survey efforts near affected areas to expand.
For more information, including identifying some common diseases that are often confused with beech leaf disease, see Michigan.gov/Invasives/ID-Report/Disease/Beech-Leaf-Disease.
Michigan’s Invasive Species Program is operated cooperatively by the Michigan Departments of Agriculture and Rural Development; Environment, Great Lakes and Energy; and natural resources.
/Note to editors: Accompanying photos are available for download below. Credits and suggested subtitles follow.
Brown Leaf: Dark streaks may remain visible on affected leaves in winter. Photo courtesy of Ontario Ministry of Natural Resources Forestry.
BLD Map: Beech leaf records in US and Canadian counties through July 2022. Map courtesy of Cleveland Metroparks.
Withered Leaves: Thick bands of leaf tissue may turn yellow late in the growing season./