 The sycamore is susceptible to sooty bark disease , caused by the fungus <unk> <unk> . This causes wilting of the crown and the death of branches . Rectangular patches of bark become detached exposing thick layers of black fungal spores . The fungus may be present in the heartwood without symptoms for many years , working its way towards the bark following long , hot summers . The spores are hyper @-@ allergenic and cause a condition called maple bark stripper ’ s disease , a hypersensitivity pneumonitis . Less serious is the fungus <unk> <unk> which often forms the disease known as tar spot , in which black spots with yellow margins form on the foliage . The leaves may fall prematurely but the vigour of the tree is little affected . Sycamore leaf spot , caused by the fungus <unk> <unk> , results in pale blotches on leaves which later dry up and fall . This disease can cause moderate leaf loss but trees are little affected in the long run . 
