Description contributed by Graham Kinsey, CABI, based on Wehmeyer (1933).
Anamorph: Phomopsis denigrata (Desm.) Traverso (1906). Conidiomata ca 400 µm diam. Conidiophores 15-24 x 1-1.5 µm. Alpha-conidia 8-12 x 2-4 µm, fusoid.
Teleomorph: stromata host surface usually blackened over wide areas, ventral zone usually present along pith. Ascomata scattered singly, ostioles erumpent singly and numerous, short-cylindrical or merely papillate. Ascospores 12-15 x 2.5-3.5 µm, usually long and narrow, not constricted and tardily septate.
Wehmeyer considered this to belong within the D. arctii aggregate. The spores are tardily septate and often lacking a septum, but most are 4-guttulate.