Description adapted from an unpublished document by Graham Kinsey, CABI, based on Wehmeyer (1933).
Anamorph: Phomopsis systema-solare (Naumov) Gvirt. & Ratiani (1973). Conidiogenous cells to 30 µm long. Alpha-conidia 6-10 x 1.5-3 µm.
Teleomorph: stromata on the host surface as clusters of ostioles grouped around a minute perforation of the periderm which exposes a blackened ectostromatic disc 0.2-0.4 mm diam, often when the periderm is thin and transparent the blackened zone in the bark appears on the surface. Ascomata 400-725 µm diam, irregularly spherical, occurring singly or in groups of 2-8 within pustulate areas 1-4 mm diam, separately erumpent through the periderm usually around a central cushion of ectostromatic tissue, ostioles black papillate and separate. Asci 110-145 x 18-21 µm, clavate, with a conspicuous J- refractive apical ring. Ascospores 35-55 x 7-9 µm, fusiform-cylindrical, usually curved or bent at the septum, constricted at the septum, often with a gelatinous appendage ca 2 µm diam. and 2 µm in length at each end. In some collections a proportion of the ascospores are 3-septate and range in length to around 75 µm.