Bactrodesmium betulicola
Anamorph: Conidiomata absent. Colonies forming compact blackish, usually shining sporodochia 100-300 µm diam. on the host bark. Mycelium immersed in the substratum, composed of branched, septate, subhyaline to brown hyphae 1.5-5 µm diam., forming a compact pad-like structure from which the conidiophores develop. Conidiophores hyphal in nature, to 40 µm long and 1-3 µm diam. but very variable in length, flexuous, often branched, especially towards the apex, subhyaline or pale brown, sometimes vesiculose at the apex. Conidiogenous cells not clearly differentiated from the conidiophores, and proliferation not evident. Conidia 26-40 × 9-15 µm, formed singly, terminally and at the ends of branches, rather variable in form but usually cylindrical to cylindric-ellipsoidal, the apex rounded and the base obtuse to truncate, the secession scar 2-3 µm diam; dark brown, 4-septate, the septa thick-walled and the lumina semi-occluded (distoseptate), the end cells much paler and thinner-walled.
Teleomorph: Unknown.
Not formally assessed, but probably much more common than the available records indicate due to its inconspicuous nature. 10 records in FRDBI (accessed Dec 2017).
On dead bark of Betula spp., with one record from Alnus that needs confirmation.
Scattered throughout England, with a single record from southern Scotland.