Description contributed by Graham Kinsey (CABI).
Dorsal zone distinct, sometimes extending along the wood surface between perithecial groups and sometimes exposed from above, ventral zone a sharp black line deep in the wood enclosing an entostomatic area in which one or several perithecial groups are situated.
Anamorph: conidiomata 600-950 x 500-600 µm, locules 400-475 µm high at the center and tapering to the edges. Conidiogenous cells 3-26 x (1-)1.5-2(-2.5) µm, arising directly from the cells lining the locules. Alpha-conidia (4-)5-8 x (1-)1.5-2(-2.5) µm, fusiform-narrowly ellipsoid; beta-conidia 14-21(-25) x 1 µm, filiform; with intermediate forms.
Teleomorph: ascomata 0.3-0.8 mm diam., occurring singly or compactly grouped, ostioles prominent or not, convergent, cylindrical and erumpent through the dorsal zone. Interascal tissue composed of paraphyses 5 µm wide, septate, gelatinizing at maturity. Asci 43-60(-65) x 4-6.5(-8) µm. Ascospores (10-)10.5-16(-18) µm x (1.5-)2.5-3(-3.5) µm, narrowly ellipsoid-cylindrical, later becoming 1-septate.
Close to D. beckhausii. The only GB & I record is of the anamorph. The teleomorph is characterised by narrow truncate asci and narrow cylindric-ellipsoidal ascospores.
On Betula pendula.
Only one record. Scotland (Aberdeen region).