This picture was taken last Sunday on our walk on Shean Mountain. It appears to be a Bracket Fungi which feed on wood, either living trees or dead logs, the brackets are the fruiting bodies. These form shelf-like structures singly or in groups and normally stick out from the trunk or branches though some can develop from infected roots and appear at ground level.
There are many different species of bracket fungi and they can vary in size from a few cms to a giant polypore (Meripilus giganteus) which can reach 1m across. Some species are specific to a particular host, ash and beech trees are both very susceptible to specific bracket fungi. Some of the other more interesting specimens include the gruesome “beefsteak” fungus that looks like raw meat and produces red juice when cut and the more attractive “chicken of the woods” which is bright yellow and a gourmet delicacy.
(But don’t take my word for it!!!)
Bracket fungus causes severe damage to trees. The first external symptom of infection, (often the appearance of the bracket fruiting bodies on the trunk or main branches), may be preceded by visible crown thinning and die back. By the time the bracket appears there will already be extensive internal heartwood decay. Decay usually leads to weakening and eventual breakage or wind fall of the tree.