Armillaria Root Rot

Characteristics

Armillaria root rot is a fungus that is typically present in the soil, and becomes aggressive when a tree is subject to unfavorable growing conditions. Being an opportunistic pathogen, Armillaria will colonize trees with drought stress, soil compaction, wounding of roots, nutrient deficiencies, insect defoliations, and other fungal infections.

An infection will begin when the fungus, living in the ground, sends out string-like growth that invades healthy roots, root collars, and the lower trunks of trees. In the fall spores are dispersed by the wind and carried to other trees. Armillaria root rot feeds on both living and dead tree tissues.

Signs & Symptoms

Trees with Armillaria root rot may not show external symptoms. In an infected tree, upper foliage may become sparse, and canopy dieback may occur. Sometimes canopies can still appear healthy even though a tree is infected. Infected trees usually show a soggy, whitish layer of fungal threads, between the surface of the inner and outer bark. In the fall, clusters of overlapping honey-coloured mushrooms appear at the base of trees or on the adjacent soil surface. Armillaria root rot will often kill solitary trees, but may spread to adjacent trees through the ground.

Armillaria will rot the roots, root crown, and lower stem of infected trees. Trees with compromised roots tend to fail at the base during windy conditions.

Treatment & Recommendations

Prevention is the best ways to protect your tree, and to avoid the conditions in which the disease will flourish. Properly watered trees with proper nutrition tend to be less prone to infection. Avoid re-planting at a location from which a diseased tree has been removed, since this fungus can persist in the ground for many years.

If your tree has mushrooms growing on or near it call our office. One of our qualified arborists can assess your tree for signs and symptoms of Armillaria root rot.