Beech Bark Disease

White spots on the bark of beech trees is a clear indication of Beech Bark Disease
An infected beech tree showing characteristic white spots on the bark.

U.S. Forest Service photo

The American beech, a dominant species in the upland forests of Pictured Rocks National Lakeshore, is seriously threatened by Beech Bark Disease (BBD). This tree disease originated in Europe and was accidentally introduced to Nova Scotia around 1890, most likely from infected European beech brought for a horticultural exhibit. It has been spreading slowly through the eastern United States ever since.

Beech bark disease was first detected in Michigan in 1990 and discovered at Pictured Rocks in 2001. Advanced primarily by wind, BBD has moved from east to west through the national lakeshore. Biologists estimate that 80 to 90 percent of the park's mature beech trees will not survive.

Beech bark disease is the result of a complex interaction between three non-native pests (a tiny scale insect and two species of Nectria fungus) and a native Nectria fungus. The beech scale insect wounds the tree by piercing the bark with sharp mouth parts and sucking out the sap. Nectria fungus is then able to enter and infect the tree through these wounds. Once infected, most mature beech trees weaken and die slowly over the span of several years. Older and larger trees are more susceptible to BBD than younger ones.

Infected trees can be recognized by obvious fuzzy white "cotton ball" bumps or other white patches on the bark. The white color is caused by waxy secretions from the scale insects. Other signs include dark cankers on the bark, loss of leaves, broken branches, and discolored foliage. Healthy beech trees have smooth grey bark and dark green shiny leaves. Beech bark on older trees is often covered with patches of lichen and/or moss, which are harmless and should not be mistaken for BBD.

The loss of beech trees to BBD will affect many animal that depend on nutritious beechnuts for food

Ohio Dept. of Natural Resources photo

Impacts to the Forest Ecosystem
The majestic beech is one of the dominant trees of northern hardwood forests along with maple, yellow birch, and hemlock. It is the major nut-producing tree in this ecosystem, and its loss will affect wildlife such as black bear, squirrels, chipmunks, porcupines, white-tailed deer, and birds that depend on this food source. Beech trees are also a favorite nesting site for chickadees, and they provide shelter for woodpeckers, fishers, martens, and other cavity dwellers.

As infected beech fall and die, they create a gap in the forest canopy. Thickets of young beech (sprouting from roots) and saplings of other species will quickly take advantage of the increased space and light to fill in these forest openings.

The change from a closed-canopy forest to a more open one will affect animal populations as well. Increased understory vegetation and woody debris from downed beech trees will favor certain species over others. Hawks and other birds that prefer a dense canopy may no longer nest here. The loss of beech in this forest will have far-reaching impacts that scientists are only beginning to understand.

Park researcher inspecting a marked potentially resistant beech tree in the backcountry.
Park researcher inspecting beech tree that appears to be resistant to BBD. This tree is covered with harmless moss and lichen growth but so far shows no sign of scale insect infection.

NPS photo / Mike Peters

What can be done?
The sheer number of beech trees throughout the park (40 to 60 percent of some forest stands) makes treating BBD both uneconomical and unrealistic. No large-scale pesticide application or biological control methods currently exist.

Beech saplings will always be present in the forest since they can sprout from roots of fallen trees, but the vast majority of them will become infected as young trees. The only way to restore beech as a functional component of the forest ecosystem is to identify and propagate resistant trees. Pictured Rocks National Lakeshore is taking a major role in this effort.

For the past few years, park staff have been searching for mature beech trees in the lakeshore that do not appear to be infected. Plant material from these resistant trees will be grafted onto rootstock grown from seed and the genetic characteristics of the resistant beech will take hold in the new plant.

Seedlings will be grown in greenhouses and then transferred to monitored plots throughout the lakeshore. Continued cross-breeding through subsequent generations will result in trees that are both resistant and hardy. Young trees grown from resistant stock offer the best hope of preserving beech as a dominant presence in northern hardwood forests.


Safety First
While traveling through the park, you may notice areas where dead beech have fallen or have been cut down. Pictured Rocks staff continually identifies and removes hazardous beech trees around roads, developed campgrounds, and other high-use public areas.

Visitors are urged to use caution when hiking or camping in the backcountry. Be alert for standing trees that display signs of weakness such as large, dead branches. Weakened trees may fall without warning, even on days with little or no wind. This is known as "beech snap."

Be safe and pay attention to your surroundings.


Last updated: November 18, 2021

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