Beech Leaf Disease in Pennsylvania

This summer, a concerned resident asked me to come to look at a large stand of American beech trees (Fagus grandifolia) in a forested area of eastern Berks County because he was concerned that they may have a disease new to PA, beech leaf disease (BLD). He was right. The trees looked bad, and we collected samples and sent them to the Penn State Plant Disease Clinic. I received confirmation in mid-August that the trees did indeed have BLD.

BLD is so new that we do not know much about it yet. It was first discovered in 2012 in one Ohio county along Lake Erie's southern shore. It has progressed since then, and now in 2022, it has been found in most counties in Pennsylvania. BLD affects American beech and can also affect European beech trees. Small trees can die in 3-5 years. Currently, it is unknown how BLD will affect large, mature beech trees, but some people have reported tree death within seven years.

Initial BLD Observation map from dontmovefirewood.org

Experts have found Litylenchus crenatae, a microscopic roundworm (a nematode) associated with BLD. They have also found bacteria and a fungus in the affected tissue, which may also contribute to the disease. Short-distance transmission may occur through root grafts, rain splashing, or bird movement. Long-distance transmission is thought to occur by moving contaminated plants.

Symptoms of BLD include darkening and thickening of the tissue between leaf veins that is most visible when viewed against the light sky. Photo: Emelie Swackhamer, Penn State

If you think you have found BLD on your property, you should contact your local Department of Conservation and Natural Resources service forester using the list available there.

Can you protect beech trees from this disease? It probably is not economically feasible to protect large stands of wild beech trees. However, suggestions for protecting specimen beech trees are starting to emerge from research experiments in Ohio. According to a report from the University of Rhode Island, an experimental method of treating American beech saplings with a phosphite product twice a year for five years has shown some encouraging results. According to the Connecticut Agricultural Experiment Station, another interesting possibility is a systemic product called emamectin benzoate, a restricted-use pesticide, which is labeled for use against the pine wilt nematode, as well as other pests. Research is underway, so stay tuned for more information as results are published.

Sources:

• Beech Leaf Disease
• A Small Organism Causes Big Problems for Beech Trees
• Beech Leaf Disease Treatment
• An Overview of Beech Leaf Disease