Lecanora compallens

Zeora compallens is a species of corticolous (bark-dwelling) crustose lichen in the family Lecanoraceae. It is usually found on the bark of roadside and other open-grown trees, where it often develops as a sterile, powdery crust. The species can be recognised in the field by its grey-green, warty surface and the yellowish to pale green soredia that spread across much of the thallus. It has been recorded from western and central Europe and is also known from parts of eastern Europe and western Asia....read more on Wikipedia.