Sap-groove lichen Bacidia incompta

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A lichen has a grey-green crust.

Its brown or black fruits resemble small dots.


It used to grow in a number of places scattered around Britain, but in the last thirty years it has declined dramatically, due to air pollution from sulphur dioxide followed by Dutch elm disease. However, it has recently been found on different trees such as Sycamore and Beech in the New Forest and Dorset, and is still present on some surviving elms in Scotland.


Trees, particularly elms, in open situations such as hedges or parklands.

Key threats

The main threats now are the continuing effects of Dutch elm disease, clearance of mature trees and pollution from the spray drift of agrochemicals.