16 VIRGINIA FORESTS Beech leaf disease is associated with a nonnative, microscopic worm, also known as a nematode (Litylenchus crenatae subspecies mccannii), that is otherwise only found in Japan. Research is still ongoing to determine how the nematode spreads, but rain and wind appear to facilitate its movement throughout a forest. The nematode has also been found in mites that can live on birds, which may serve as a mechanism of dispersal. Since beech leaf disease is a relatively new disease, there is little research on the impacts of The compounding effects of beech bark disease and beech leaf disease on American beech in a forest in northern Maine. the disease to the surrounding ecosystem. The disease causes a reduced canopy that increases light to the forest floor, which may influence the understory community composition. In addition, the disease reduces the overall photosynthetic capacity of the tree. Compounding disease effects The distribution of beech bark disease and beech leaf disease began to overlap in 2017, and beech leaf disease continues to spread to areas in the northeast that were first impacted by beech bark disease. While beech bark disease only infects larger DBH trees, beech leaf disease can impact beech trees of any size. Therefore, it could be possible that the combination of the two diseases may result in the eradication of American beech from native forest ecosystems; however, additional evidence and research on the impacts of both diseases must be gathered before making such claims. Treatment and prevention There are currently no treatment options available for trees impacted by beech leaf disease, but research on treatment options is ongoing by Davey Tree and Bartlett Tree Experts in collaboration with Cleveland Metroparks. Insecticides are available to control beech scale and prevent beech bark disease on landscape trees, but such treatments are ineffective for use at the forest scale. The most effective methods to control forest diseases are detecting disease early in order to prevent its spread and selecting for host resistance. Presently, there is evidence of beech bark disease resistant American beech, but research on beech leaf disease resistance has not yet been explored. Research is ongoing by scientists at universities and at the U.S. Forest Service to learn more about beech leaf disease to protect the eradication of yet another foundational tree species. Carrie Fearer is an assistant professor of forest health in the Department of Forest Resources and Environmental Conservation (FREC) in the College of Natural Resources and Environment (CNRE) at Virginia Tech. Her research program covers a broad range of topics related to forest health, including forest pathology, early disease detection, and the role of microbes in tree health. Dr. Fearer is broadly interested in developing rapid, non-destructive methods to identify tree diseases prior to spreading and disease resistant trees to protect forest biodiversity and assist in ecosystem restoration applications.
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