black' root' rot"
1. any of several diseases of plants characterized by black or brown lesions on the root.
2. a common disease of the apple caused by the fungus Xylaria mali.
3. a disease of tobacco caused by the fungus Thielaviopsis basicola and characterized by retarded growth and wilting.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.