Beech Bark Disease (BBD)
Beech bark disease (BBD) has been killing American beech (Fagus grandifolia) trees in the eastern United States since the 1930’s.
The disease is actually an interaction between the beech scale (a non-native insect) and either one of two Nectria fungi.
One fungus (Nectria galligena) is native and commonly causes perennial “target” cankers on stressed hardwood trees including black walnut, sassafras, and black birch. The other fungus (Nectria coccinea var. faginata) is a non-native pathogen. The fungal pathogen infects bark wounds created by the scale insects. BBD is native to Europe and first appeared in the U.S. in Maine around 1932. It has slowly spread south and has killed beech trees in WV, PA, NY, NJ, ME, TE , MI and NC. The scale insect was discovered in Michigan in March of 2000. In 2001, it was determined that beech trees in Michigan were being killed by the BBD complex. This is the first report of the disease in the Great Lakes Region.
The beech scale (Cryptococcus fagisuga) was first discovered in Ohio in 1985 at the Holden Arboretum in Geauga and Lake Counties. Since that time, the area has been periodically inspected for BBD and the Arboretum set up a monitoring program for their beech trees. While the scale insect could be found, often in high numbers, the fungal pathogens that cause BBD outbreaks could not be found. Some beech trees died or snapped off in windstorms, consistent with the disease, but the fungal component remained absent from the trees. We were watching the situation in northeast Ohio closely to see if BBD developed.
In December of 2003, a US Forest Service pathologist performing an inspection for the ODNR Forestry Division, found fruiting bodies from a Nectria fungus growing on beech tree bark at the Holden Arboretum. Beech bark disease has finally been confirmed in Ohio. The fungus isolated from the trees at the Holden Arboretum is the non-native Nectria coccinea var. faginata.
The beech scale excretes a white waxy covering while feeding on beech bark. This is quite evident during the spring and summer. The fungus produces reddish spores on the bark, which can be best seen in the autumn.
While the scale insect can be controlled with insecticides on ornamental trees, there are no cost effective control measures for forest trees.
Some beech trees (1 - 5 %) appear to have bark characteristics that are resistant to beech scale infestations. These trees are relatively unaffected, while surrounding beech trees are killed during BBD outbreaks. U.S. Forest Service scientists are trying to determine if this resistant bark characteristic is an inherited trait.
Currently, preservation of healthy beech trees is recommended in outbreak areas. Detection surveys for beech scale and beech bark disease will be expanded in Northeast Ohio in 2004.