Anamorph: conidiomata acervuli, 1-3 mm diam., abundant, subperidermal, scattered, separate, rarely confluent, rupturing the periderm, punctiform to disciform or effuse, rarely pulvinate, dark brown, composed of thin-walled vertically-arranged ± hyaline pseudoparenchyma, becoming more irregular and thicker-walled towards the base. Conidiophores formed from the upper cells of the acervuli, 20-140 X 3-6 µm, cylindrical, branched at the base, erect or flexuous, hyaline to pale brown, paler towards the apices, septate, merging indistinguishably into the vertically-arranged pseudoparenchyma. Conidiogenous cells holoblastic, annellidic, integrated, hyaline to pale brown, cylindrical with usually a single annellation. Conidia (40) 57-72 (-90) X (12-) 13-16 (-18) µm, formed singly from the apex of each conidiogenous cell and subsequent proliferations, narrowly fusiform, only rarely clavate, straight or gently curved, tapered gradually towards the obtuse apex which has a hyaline tip, also tapered gradually towards the truncate base which often carries away part of the conidiogenous cell at secession, medium brown, smooth, 5- to 7-distoseptate, many septa dark brown and prominent, cell lumina considerably reduced and enclosed occasionally in a secondary dark brown layer, apical cell usually darker than the rest, without a gelatinous sheath or appendages.
Teleomorph: appearing on the surface as conic to flattened pustulate ruptures of the periderm 1-2 mm diam., with a central angular black carbonaceous disc 0.5-1.5 mm diam. which eventually crumbles away and leaves an irregular perforation. Ostioles irregularly papillate, but usually not visible. Ectostroma brown-black, truncate-conic, fused with the entostroma. Ascomata perithecia, 300-500 µm diam., clustered in the entostroma with a rich proliferation of brown-black fungous parenchyma at maturity and often outlined by a blackened ventral zone. Interascal tissue of thin-walled paraphyses, sometimes evanescent at maturity. Asci 100-180 x 17-25 µm, clavate, evanescent at the base, with a thickened apical wall and a small refractive iodine-negative ring, 8-spored. Ascospores usually biseriately arranged, 42-55 (-67) X 6-11 µm, ellipsoidal to cylindric-ellipsoidal, usually 6-7 distoseptate, pale grey-brown at first and eventually becoming dark chestnut brown, the end cells darker and the septa eventually becoming strongly pigmented, the cell lumina globose to ellipsoidal, smooth, without a perispore, gelatinous sheath or appendages.
Not formally assessed, but the species is not particularly uncommon, at least in southern England.
Coryneum umbonatum is linked to the teleomorph Pseudovalsa longipes by Sutton (1975), while Pseudovalsa umbonata was considered to be the teleomorph of Coryneum depressum. That species has shorter and broader fusiform-ellipsoidal conidia and shorter ascospores with fewer septa that become dark brown at an earlier stage of development.
On dead twigs and branches of Quercus species.
In GBI, widespread in southern England, apparently becoming rarer with the most northerly record in VC66 Durham.