The Michigan departments of Natural Resources and Agriculture and Rural Development today announced the addition of beech leaf disease to the state's invasive species watch list. Invasive species on the watch list have been identified as posing an immediate or potential threat to Michigan's economy, environment or human health. These species either have never been confirmed in the wild in Michigan or have a limited known distribution. Beech leaf disease is associated with the microscopic worm Litylenchus crenatae, a nematode that enters and spends the winter in leaf buds, causing damage to leaf tissue on American beech and European and Asian beech species. Infestations result in darkened, thick tissue bands between leaf veins, creating a striped effect on the leaves, leaf distortion and bud mortality. Trees weakened by leaf damage become susceptible to other diseases and can die within six years. Beech leaf disease has not been found in Michigan. The disease was first discovered in Ohio in 2012. Since then, it has been identified in seven eastern states and Ontario.