The underside of the shelf is brown with millions of tiny pores in which the spores are formed. A sure sign of severe damage to the tree is the presence of the fruiting structures. Infected trees should be removed immediately. These initially form in the summer or autumn on the wood of the tree but fall off during the winter. The underside of the fruiting structure has millions of tiny pores in which the spores are formed.
New ones form on the wood the following summer and autumn.
The margin of young fruiting structures are edible but should be collected and consumed only by experts sure of their identification. The bark where the fruiting structure forms is slightly depressed and cracked. Fruiting occurs long after most of the damage has been done. Infected trees are very prone to wind breakage even before the fungus begins to form fruiting structures and should be removed at the first sign of infection. Ash, beech, cherry, butternut and walnut, elm, pine, spruce, maple, oak, and locust among others are susceptible.