Black bootlace fungi, which smells like mushrooms, is present under the dead bark.
The disease is well known among gardeners as honey fungus or 'bootlace' fungus and is at the top of the list of the disease enquiries received at the Members Advisory Service at RHS Garden Wisley.
In some places, the parasitic honey fungus (also known as bootlace fungus) is tremendously common.
Besides direct damage from acid deposition, damage can also be indirect, for example, from the bootlace fungus (honey fungus) that can kill trees.