Description: This crustose epiphyte is at its best on mature trees in former parkland landscapes or old woodlands where the pale green to grey-green thallus is marked by the presence of isidia-like surface granules flecked brown or grey above. Discs resemble those of B. laurocerasi (described elsewhere) but are larger (to 0.3mm diam.) orange-brown to almost black. Sterile B. rubella is similar though it is perhaps most frequently confused with B. caesiovirens which is more oceanic, very rare in Ireland (west Donegal and Londonderry only) and has bluish-green granules bearing abundant hair-like projections. Reactions negative. Northern Ireland; rare elsewhere.

Key Identification Features:

• Crustose epiphyte with pale green thallus of isidia-like granules, brown or grey above. Mature deciduous trees in woodland
• Never with a bluish pigment or hair-like projections from the granules (x10 hand lens).

Original text submitted by Vince J. Giavarini

Distribution Map from NBN: Bacidia biatorina at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Bacidia biatorina at iNaturalist World Species Observations database.