Beech bark disease confirmed in Door County

Be on the lookout for beech trees covered in white wool. Report suspect trees or stands to the local DNR office or to DNR Forest Health staff.

The first finding of beech bark disease in Wisconsin has been confirmed in Door County according to plant disease specialists from the Departments of Natural Resources (DNR) and Agriculture, Trade and Consumer Protection (DATCP). Agency specialists were alerted to possible presence of the disease by an observant private citizen.

Beech scales on bark - WDNR Photo by Bill McNee

Beech bark disease and the insect associated with the disease are both considered invasive species native to Europe. The nearest known location for the disease before the Door County confirmation was near Norway Michigan.
Citizens asked to not move beech logs or firewood

Forestry officials do not know at this time how the disease or the insect arrived in Door County but both can travel long distances on infested beech logs and firewood. The disease causing element can be one of several species of fungi of the genus Nectria. The insect belongs to a class of forest insects identified as “scale”, named after a waxy protective substance the bug secretes that resembles scales of a fish. Scale insects are generally parasites of plants, feeding on sap. It is the scales’ feeding on the bark that makes the tree susceptible to infection by the fungus.

During October and November DNR investigators will survey the infested area and other areas where beech is present to determine the extent of the infestation. Following completion of the survey work officials will hold a public meeting with landowners to present survey findings and discuss management options.

Although not a major component of Wisconsin forests the beech tree is an important source of food for wildlife within its range. Eastern Wisconsin is at the western edge of the naturally occurring range of the American beech tree. The most recent forest inventory estimated the Wisconsin beech tree population at about 16.6 million trees. Door County has about 1.8 million beech.

The disease is fatal to about 95 percent of the trees infested. Somewhere between one and five percent show natural resistance to the disease according to DNR forest pest experts. This slight percentage of natural resistance offers a chance for arborists to culture disease resistant strains of beech to replace trees lost to the disease. This process will likely take years say officials.

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