Shoot- and twig-dieback of mostly young plants of maples, showing a sharp border between the light brown discolored dead parts and the living parts below; on the bark surface of the dead shoots shining black, flat and roundish spots, composed of spores (conidia), which are expelled in high numbers; the conidia are pear- to club-shaped, dark brown and show several cross- and length-walls; they are rather large (up to >50 Micron in length). Possibilities of errors if there are black spore masses on bark of maple - Sooty-Bark disease of Maples.
Affected tree species
Species of Stegonsporium are rather weak pathogens following various mechanical damage or stress (light deficiency). They cause only slight dieback of shoots, twigs or rarely branches. Among the species reported for Austria Stegonsporium pyriforme, sexual stage Prosthecium pyriforme is most common on Acer pseudoplatanus. The same host is colonized by another species(Stegonsporium sp., sexual stage Prosthecium galeatum), but a distinction fromStegonsporium pyriforme requires microscopical investigations. A third Stegonsporium-species belongs to Prosthecium opalus occurring only on Acer opalus.
Curative measures Commonly none necessary
Stegonsporium: dieback; in the lower part of the dead shoot the black spore masses are visible
Stegonsporium: masses of spores (conidia) on the surface of a maple-twig