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Guide to Beech Leaf Disease for the Public

Beech Leaf Disease is spreading rapidly in our region and poses a major threat to Pennsylvania's beech trees. Learn about identification and current management options.

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Updated:

August 29, 2024

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Leaf striping, as seen from below, is a symptom of beech leaf disease (Photo: Yonghao Li, The Connecticut Agricultural Experiment Station, Bugwood.org)

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What You Should Know

Beech Leaf Disease (BLD) poses a substantial threat to beech trees in the eastern United States, affecting all types of beech trees, including our native beech, Fagus grandifolia, and European beech trees, Fagus sylvatica. The disease is caused by a foliar nematode, a type of microscopic roundworm, that feeds inside the leaf buds of beech trees. When the leaves emerge, they have a characteristic striped appearance, and may become curled, leathery, or withered as the season progresses. Over time, the canopy will thin as it loses leaves, and the tree will no longer be able to photosynthesize, causing it to die. Small saplings may succumb to BLD in a year or two, while larger, more mature trees can die within 7 to 10 years. Unfortunately, the disease has already spread rapidly in our region and is currently found in all 67 counties in Pennsylvania.

Symptoms

Early in the infection, you may notice dark bands or stripes forming between leaf veins, as shown in the photo above. The easiest way to check American beech trees for BLD symptoms is to stand under the canopy on a sunny day. The leaf striping will be most obvious when looking up at branches from below. European beech trees and American beech cultivars with dark foliage also develop the leaf striping, but it can be more difficult to see. European beech symptoms often include a blighted appearance similar to anthracnose.

Beech tree leaves with stripes between veins — Photo: Matthew Borden, Bartlett Tree Experts, Bugwood.org

Later in the infection, leaves will develop a thick, leathery texture and may start to shrivel. Eventually, the lack of bud development and healthy leaf production will cause the tree canopy to thin and die back.

Green leaves with yellow striping and leaf curling. — Photo: Matthew Borden, Bartlett Tree Experts, Bugwood.org

Current Management Options

Research into effective management options for beech leaf disease is in its early stages and is ongoing. As new research becomes available management recommendations are likely to be updated. Initial research and plant health care (PHC) providers’ experience has shown that using phosphite fertilizers can help boost the vitality and natural defenses of beech trees and may also inhibit nematode activity in the tree, helping to suppress beech leaf disease. A recent study showed that applications of the nematicide/fungicide with the active ingredient fluopyram (registered for ornamental use as "Broadform") reduced nematode populations substantially over three years. A fungicide with the active ingredient thiabendazole hypophosphite (registered for ornamental use as "Arbortect 20S") which has been commonly used to help protect elm trees from Dutch Elm Disease, has been shown to have nematocidal properties and has also been reported by PHC providers to show positive results when treating for beech leaf disease. While these treatments may help individual trees in ornamental landscapes, there is currently no cost-effective treatment available for beech trees in forest settings. It is important to remember that research on this topic is relatively new, and treatment recommendations could change and improve with time. Trade names listed are not an endorsement by Penn State Extension but are provided as examples of available registered materials.

What to Do Next

If you suspect BLD, collect fresh twigs and leaves showing a range of symptoms in a gallon bag and send a sample to the Penn State Plant Disease Clinic to confirm the diagnosis.
Once you receive a positive diagnosis, you can work with a local arborist to determine the best course of action for your property. To find an ISA-certified arborist in your area, you can use this online tool.
If you own or manage forestland that may be impacted by BLD, you can contact your local. DCNR Service Forester for help creating a management plan.
As always, you can reach out to your closest Penn State Extension county office for resources and materials about identifying and managing BLD. Master Gardeners and Extension Educators are on hand to answer your questions about BLD.