Rhizoctonia is a common soil fungus which attacks a wide variety of plants and is not specific on strawberries as is red stele.
Black root rot is more severe when lesion nematodes are present.
The characteristic action of this fungus is to destroy the fine feeding roots, causing the plant to show symptoms of drought and low nutrition. The plant may not die. The infected roots show a dry, brown decay of the fleshy part of the root, which finally is entirely disintegrated. The central cylinder remains enclosed in a tube of the root epidermis like a wire running through a pipe. Black root rot is difficult to control.