Description contributed by Graham Kinsey, CABI, based on Wehmeyer (1933).
Anamorph: Phomopsis rudis (Fr.) Höhn. (1906). Alpha-conidia 6-7 x 2 µm; Beta-conidia 21-30 x 1.5 µm.
Teleomorph: stromata forming pustulate ruptures of the host periderm with ostioles erumpent singly or in loose divergent clusters, surface of bark heavily blackened, with irregular ventral zones within the wood. Ascomata 200-500 µm diam, usually in small groups, ostioles usually long-filiform sinuous and appressed against or running beneath the periderm. Asci 40-47 x 6-9 µm, clavate, with a refractive apical ring. Ascospores 10-13.5(-15) x 2.5-4 µm, fusiform-ellipsoidal.
The above description is of Wehmeyer's host-restricted typical form on Laburnum.