Beech bark disease (BBD) is a devastating and fatal disease complex which affects American beech (Fagus grandifolia) as well as ornamental beech species (European beech, Fagus sylvestris and others). BBD was accidentally imported into Nova Scotia, Canada around 1890 on ornamental beech. Since then, it has been spreading slowly southward throughout the eastern United States. Humans also contribute to disease spread by transporting firewood.
BBD is caused by an exotic, invasive sap-feeding scale insect and a fungal pathogen. The insect pest, a small, white, fuzzy beech scale (Cryptococcus fagisuga) wounds the tree by piercing the bark with sharp mouth parts and sucking out the sap. The many wounds created by the scale insect allow the lethal fungus, Neonectria faginata, to enter the tree and cause disease.
Once infested, most beech trees weaken and die slowly over the span of several years to decades. Older, larger trees are more susceptible to BBD than those which are smaller or younger. Affected trees can be recognized by waxy-white patches on the bark or fuzzy “cotton ball” bumps. Severe infestations of beech scale make the tree look like it has been rolled in powdered sugar (see above photo). Other symptoms include loss of leaves, dead or broken branches, and discolored, yellowing leaves. The Neonectria fungi are uncommon to see, but when present, form clusters of tiny, scarlet red fruiting bodies which may be visible on the bark.
The American beech is a dominant species in the upland hardwood forests of the eastern United States. Beech can be identified by its characteristic, smooth, light grey bark. It is a major nut-producing tree, and its nutritious beechnuts provide food for black bear, chipmunks, squirrels, porcupines, white-tailed deer, and a variety of birds, including ruffed grouse. As beech trees decline, loss of this food source will likely have a profound effect on wildlife. Beech are also favorite nesting sites for chickadees, and they provide shelter for many other cavity dwellers such as owls and woodpeckers. BBD is being closely monitored in the Shenandoah National Park as it spreads through the Appalachian mountain chain.
Treatment options to date are limited in efficacy. In residential areas, beech scale may be physically removed from bark using soapy water and a soft brush. Additionally, applications of horticultural oil are effective, but require complete coverage which may be difficult on larger trees. Researchers are currently working to identify resistant trees in areas which are heavily affected by BBD. These BBD resistant trees are then used for breeding trials and clonal reproduction to enhance the survival of the species.
In Fairfax County, American beech trees make up about 10% of the urban forest and are common overstory trees in natural areas throughout the county. BBD has not yet been identified in Fairfax County. The closest confirmed BBD incidence is in Shenandoah National Park. Staff is conducting long-term monitoring of beech forests in the County before BBD arrives.
Residents can help urban foresters by keeping an eye out for BBD and beech scale when hiking in the woods. If you see a beech tree that looks like it is covered in powdered sugar, give us a call at 703-324-1770 or email a picture to firstname.lastname@example.org. To help keep the disease from spreading further, please do not move firewood.
SIGNS AND SYMPTOMS OF BEECH BARK DISEASE
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