Department Resources

Beech Leaf Disease

American Beech Tree

American beech (Fagus grandifolia) native to eastern North America, is a beautiful hardwood forest tree known for its smooth gray bark. Beech trees are critical to the native forest ecosystem. They provide food to a wide variety of wildlife including deer, small mammals, turkeys, and many other native birds. A hard mast tree, their fruit is a nutrient-dense nut, rich in essential fatty acids, vitamins, minerals, and proteins. These seeds last through the winter and serve as a food source when other plants have long stopped producing fruit.

Not only are American beech very beautiful trees, but they are also tied with red maple for the County’s most common tree species. According to an analysis conducted by the UFMD, there are approximately 4.3 million beech trees in the County, approximately 9% of all trees. Beeches are also a familiar ornamental tree in urban landscapes.

American Beech Leaves, photo credit Rob Routledge, Sault College, Bugwood.org — American beech leaves, photo credit Rob Routledge, Sault College, Bugwood.org

American beech fruit (nut), Bill Cook, Michigan State University, Bugwood.org

Beech Leaf Disease observed in Burke Lake Park

European beech leaves, Robert Vidéki, Doronicum Kft., Bugwood.org

Beech Leaf Disease (BLD) is a new disease of native American beech (Fagus grandifolia) as well as the commonly planted European beech (Fagus sylvatica), and some other Fagus species including ornamental cultivars such as copper, purple, golden, weeping and fern-leaf beech.

The disease is caused by a foliar-feeding nematode (a microscopic roundworm), Litylenchus crenatae subsp. Mccannii which is species-specific to beech trees. The nematodes enter the tree’s leaf buds in the fall where they overwinter, multiply, and feed on newly forming leaf tissues. The nematodes and the damage they have done are already present in the leaves when they expand in the spring. The nematodes multiply and spread throughout the tree from year to year until leaf buds no longer produce leaves. As healthy foliage decreases, the tree’s energy, nutrient, and water uptake decreases, and the tree eventually dies. BLD is nearly one hundred percent fatal. Seedlings and saplings die in one to three years; more mature trees in four to ten years. A small percentage of beech has shown resistance, but BLD has the potential to drastically alter the composition of forests in the eastern US. Research is ongoing to fully understand this disease.

BLD Nematode, photo by Paulo Vieira, USDA, ARS — *BLD Nematode, Photo Credit: Paulo Vieira, USDA-ARS*

Scientists are comparing these nematodes’ DNA with that of similar nematodes native to Japan to determine if that is its origin.

Life stages of the Beech Leaf Disease Nematode, Photo Credit: Paulo Vieira, USDA-ARS

Recent research shows that the nematodes that cause BLD are likely spread by birds, insects, rain and wind, and that other microscopic organisms may be involved. They move on water films on the tree and have been found in the leaf litter under infected trees. People can unknowingly introduce them to new areas by moving infected beech tree seedlings, saplings, tree parts, and leaf litter.

BLD was first identified around Cleveland, Ohio in 2012, and has subsequently spread into Michigan, Ontario, New England, New York, Pennsylvania, West Virginia, Northern Virginia, and Maryland.

In Fairfax, it has been found in several locations including Burke Lake Park, Pohick Stream Valley Park, Lake Mercer, NOVA Parks near Bull Run creek and the Occoquan River.

The symptoms of the disease first appear on leaves as dark green, interveinal stripes. It is usually identified first on saplings and the lower foliage of larger trees. Infected leaves may also become puckered, cupped, leathery or distorted. Some leaves on a single branch may be infected while others are not. It spreads throughout the tree and from tree to tree progressively from year to year.

Other diseases of beech leaves can sometimes look something like BLD, but if you look for the dark green interveinal stripes of BLD in May-June before beech leaves are typically affected by other diseases, the diagnosis is easier. The other diseases are native and are not serious on their own because if they are present at all in any given year, it would be later in the season. They can contribute to decline when BLD has already infected the tree.

Woolly beech aphid, photo credit Petr Kapitola, Central Institute for Supervising and Testing in Agriculture, Bugwood.org< — Woolly beech aphid, photo credit Petr Kapitola, Central Institute for Supervising and Testing in Agriculture, Bugwood.org

Eriophyid mites, photo credit Linda Haugen, USDA Forest Service, Bugwood.org

Erineum mites, photo credit Eric R. Day, Virginia Polytechnic Institute and State University, Bugwood.org

Anthracnose, photo credit Nancy Gregory, University of Delaware, Bugwood.org

If you see beech leaf disease, you can report it to pestmail@fairfaxcounty.gov. Provide photos and a location with your report. You can also provide a report by phone 703-324-1770 TTY 711.

Additionally, you can report your sighting on iNaturalist. It is an easy-to-use app that shares information with other community scientists. Find directions on their website.

UCFD recommends using an Integrated Pest Management (IPM) approach to manage insects and diseases. Unfortunately, for BLD, few options are available, and they may be used only under certain circumstances.

There are no biological controls such as nematode predators or parasites. There are no cultural practices that reduce nematode establishment, reproduction, dispersal, or survival. There are no mechanical and physical controls that trap or kill nematodes directly, barriers to exclude them, or to make the environment unfavorable to them.

To date there are only limited chemical controls that are available to be used carefully and only when needed. They should be selected and applied following the label directions to minimize potential harm to people, non-target organisms, and the general environment. There are currently two chemical treatments available in Virginia. One is a trunk injection treatment, and the other is a foliar treatment. Both chemical options should only be applied by licensed pesticide applicators. In addition, potassium phosphite-based fertilizers have been shown to reduce the severity of symptoms and slow disease progression in smaller trees.

The Virginia Department of Agriculture and Consumer Services (VDACS) has issued a Special Local Need Label for Arbotect® 20-S for the treatment of beech trees for BLD. The label is temporary and will expire at the end of 2028. The product is a systemic fungicide containing the active ingredient Thiabendazole Hypophosphite and other ingredients that have been approved under FIFRA (Federal Insecticide, Fungicide, and Rodenticide Act administered by the EPA). The product must be mixed with a large volume of water in a tub then pumped out and injected through multiple injection sites into a single tree. The process can take from 2 to 6 hours per tree and the treatment may provide the tree with protection from nematode damage for 2-3 years. Because of its high cost in materials, time, and labor, trunk injections are limited to selected individual trees. It is not feasible nor is it approved for broad use in a forested setting. The advantage of this treatment is that the product application is confined to the target tree. The shedding and decomposition of tree leaves and other tree parts into the environment has not been studied.

*Example of trunk (or stem) injection system for BLD*

VDACS has also registered a foliar treatment Broadform® for treating individual trees for BLD. It is permitted under a FIFRA Section 2(ee) Recommendation and has not been submitted to and approved by the EPA. This product is a fungicidal treatment containing the active ingredients Fluopyram and Trifloxystrobin that is applied to the tree’s foliage using a hydraulic sprayer. This product is also not approved for use in a forested setting.

Notable information about this treatment:

Each tree would need 2 or 3 treatments per growing season
Spray treatments are prone to drift, so may contaminate non-target vegetation, areas prone to runoff, and adjacent properties which is prohibitive
It is intended for use on small to medium size trees
Environmental hazards as stated on the label prohibit their use near open water, stormwater drains, and where potential runoff is possible

Potassium phosphite, potassium polyphosphate, and other potassium fertilizers (0-0-27) have shown some good results in smaller trees. The product is mixed with water and applied at the base of the infected tree according to the label. It works by strengthening the cell walls of the tree leaves making it more resistant to nematode damage. The tree will likely show symptoms, but resist decline to varying degrees.

*UCFD staff recommend reading the product labels provided in this document.

Treatment Comparison Table

	Trunk Injection Arbotect® 20-S	Foliar Spray Broadform®	Potassium Phosphite Soil Fertilizer
Active ingredients	Fungicide ~ Thiabendazole Hypophosphite	Fungicides ~ Fluopyram and Trifloxystrobin	Potassium polyphosphate (0-0-27)
Appropriate Trees	Larger landscape trees with exposed root flares	Smaller landscape trees	Smaller landscape trees
Treatment frequency	Each 2-3 years	2-3 x per growing season	2 x during May-August one month apart
Treatment efficacy	Very effective	Somewhat effective	Somewhat effective
Chemical location	Inside the tree stem, branches, leaves	Tree surfaces	Soil under the tree
Expense	More expensive fewer treatments	Less expensive more treatments	Less expensive more treatments
Availability	Certified, licensed arborist	Certified, licensed arborist	DIY or arborist
Environmental impact	Very slow release through decay	Subject to drift and runoff	Very little if used according to label directions
Chemical Hazards	YES - Label must be followed	YES - Label must be followed	YES - Label must be followed

For all yard trees UCFD recommends such as proper mulching and watering during droughts. Because beech trees are shallow rooted, protecting them from mower damage and soil compaction is essential such as proper mulching and watering during droughts. Because beech trees are shallow rooted, protecting them from mower damage and soil compaction is essential.

UCFD recommends caution when considering chemical treatments. It is against the law to apply at rates above what the label specifies. When applying chemicals, the label is the law. UCFD recommends finding a licensed, certified, insured arborist: How to Hire an Arborist or Tree Care Company | Public Works and Environmental Services.

Research to find new treatments is ongoing. Currently, there are no treatments proven to be effective for BLD in forests. UCFD is tracking the spread of the disease while assisting in research efforts as staffing permits. UCFD will undertake a trunk injection treatment program limited to select amenity beech trees growing on Fairfax County property.

UFMD is monitoring the spread of BLD, tracking the latest scientific research about the disease, and participating in research projects to help find safe Integrated Pest Management (IPM) tools to manage it.

If you see beech leaf disease, you can report it to pestmail@fairfaxcounty.gov. Provide photos and a location with your report. You can also provide a report by phone 703-324-1770 TTY 711.

Additionally, you can report your sighting on iNaturalist. It is an easy-to-use app that shares information with other community scientists. Find directions on their website.

Seedlings and saplings can die within 3 years, more mature trees in 4 to 10 years.

Pest Alert—Beech Leaf Disease

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Beech Leaf Disease