Birch Tree Root Rot

Identification

• A birch tree can be afflicted with Armillaria root rot, commonly called shoestring root rot. This disease is a result of infestation by Armillaria mellea, a soil-borne fungus that includes approximately 20 species of fungi. More than 700 species of woody plants and trees, including the birch, are susceptible to this disease. It is most prevalent in areas where the soil is heavy and cool, like the Pacific Northwest of the U.S.

Significance

• A birch tree that is already stressed, be it from drought, flooding or other disease, is most vulnerable to attack from Armillaria root rot. The fungi damages the roots of the birch, preventing it from being able to properly upload water and nutrition, leading to a dieback of branches and foliage and, potentially, the death of the entire tree. It occurs most frequently in forested growth or in areas that recently had been primarily forest in nature.

Symptoms

• The development of premature fall foliage and leaf drop is an indication of the presence of Armillaria root rot, along with a yellowing and browning of leaves, stunted growth, and the death of twigs, branches and even the main trunk of the birch. In most instances, this decline occurs over the course of several years, but as the root rot advances, it may appear to speed up significantly. Decay in the lower trunk of the birch will be evident.

Final Effects

• As death of the birch nears, gum or a fermenting liquid will appear at the base of the trunk, accompanied by a collection of thin, white, fan-shaped sheets of the Armillaria fungus, emitting a strong mushroom odor. The disease is spread easily through root grafts, as the root systems of adjacent trees intertwine underground. Birch trees infected with this disease should be removed and destroyed, along with their litter. Most trees will succumb within a few years.