Beech Bark Disease (Nectria coccinea var. faginata)
Invasive Forest Pests & Diseases
Beech bark disease results from the combined actions of an non-native sap-feeding scale insect (the woolly beech scale) and certain types of fungi, mainly Nectria coccinea var. faginata . The disease arrived around 1890 in Nova Scotia on an imported European beech, and by the 1930s it was causing significant beech mortality across the Maritime Provinces. The disease (both the insect and the fungus)
has since spread outward, killing beech trees across north-eastern North America. By 2004, beech scale had been detected in Ontario as far north as the north shore of Lake Huron and to London in the southwest. The disease has since been detected in areas to the east and across the GTA and the Golden Horseshoe.
The possibility of disease arises when scale insects colonize beech trees and puncture the bark during feeding. This leaves the trees susceptible to infection by the fungus; the spores of which enter the tree through these puncture wounds. The fungus then grows inside the wound, killing the inner bark of the tree and creating a canker of dead and dying tissue. If too many wounds develop around the trunk, the tree can become girdled and die. If the fungus does not kill the tree directly, the cankers may enable other fatal pathogens and parasites to attack, or severely weakened trees may snap in the wind.
The scale insect, spread by wind, is tiny and often unnoticed until its adult stage when it produces a white woolly wax that can cover large areas of bark. The fungus usually arrives several years after the tree becomes colonized by scale at which time the scale may disappear, indicating the underlying bark has been killed by the fungus. Other symptoms include crown die-back, black or brown tarry spots on the bark, and warty cankers. The fruiting bodies of the fungus appear as small red or light orange coloured nodules at the site of the cankers, and spores are released during moist conditions. Spores are normally spread by wind and rain, but can also be spread by contact.
The loss of healthy beech trees negatively impacts species that use them, such as deer, wild turkey, black bear, and other small mammals such as chipmunks. Beech bark disease can also lead to reduced biodiversity and major changes to these forests.
To prevent accidentally spreading the disease, firewood should not be transported between July and November when the scale is active. Ornamental trees can be monitored seasonally and treated for the scale insect to prevent infection by the fungus.
