By Elly Voigt, DNR Forest Health Lab Assistant, Fitchburg
Beech leaf disease (BLD) is a destructive disease affecting beech trees in the U.S. The disease has not yet been observed in Wisconsin, but it could become an issue in the future in the eastern third of the state, which is the edge of the American beech’s native range.
Symptoms of this disease were first observed in Ohio in 2012. Since then, symptomatic beech have been observed in areas of West Virginia, Pennsylvania, New York, New Jersey, Rhode Island, Connecticut, Massachusetts and Ontario, Canada. BLD can affect our native beech, American beech (Fagus grandifolia), as well as ornamental species, including European beech (Fagus sylvatica).
Symptoms of the disease include dark striping or banding between the leaf veins (Figure 1). This symptom is best observed by standing below the tree and looking up at the bottoms of the leaves. Diseased leaves may also pucker (Figure 2), curl, become thick and leathery in texture, or develop yellow or necrotic (dead) areas. On a BLD-infected beech tree, you may see buds that never leaf out, dead twigs and branches, or a loss of leaves throughout the tree. Over several years, BLD can kill entire beech trees, especially small, young trees.
Recent research has revealed an association between BLD symptoms and the presence of a newly recognized nematode (microscopic roundworm) in the buds and leaves of beech trees. Crude extracts of these nematodes (Litylenchus crenatae mccannii) have been inoculated onto seedlings and have produced symptoms similar to those of BLD. However, the biology of BLD is not yet fully understood, and research is ongoing.
Beech trees are important in our forests for many reasons, including providing food for wildlife. If you see symptoms of beech leaf disease in Wisconsin, please contact your regional forest health specialist.
For more information about beech leaf disease, check out the Forest Service’s recently released pest alert on this topic.