The tree declines in general and the presence of the fungus is known when it produces a fruiting structure from a wound. This hard, woody, shelf-like perennial structure may attain a width of two or more feet. The upper surface is smooth, zoned, and grayish or grayish black, whereas the undersurface is white when fresh, but becomes yellowish with age. The undersurface turns brown when bruised and is a favorite medium for artists. There is no control - only prevention, by avoiding wounding of the tree.
Leaves turn brown and wilt and blighted branches die back for several inches.
Brown streaks can be seen in sections of the wood. Bacterium overwinters in the cankers, so young leaves are infected as soon as they unfold. The damage can be confused with frost injury. Prune out infected twigs and spray in early spring with an approved fixed copper fungicide. Mainly a nursery disease.