E-Flora BC: Electronic Atlas of the Flora of British Columbia

Summary:
Diplocarpon rosae forms black spots on rose leaves, and rarely minute fruiting bodies. The conidial stage, black spot of rose, is widely distributed wherever the rose is cultivated.

Distribution includes BC, WA, OR, and ID.

Upper surface:
0.025cm wide, spherical to discoid, at first closed, opening with a star-shaped aperture; conidial stage forming large dark brown or blackish spots, sometimes confluent and involving the entire leaf

Microscopic:
spores 20-25 x 5-6 microns, elliptic, colorless, unequally 2-celled, constricted at the septum; asci 8-spored, reaching length of 70-80 microns and width of 15 microns, subclavate [more or less club-shaped]; paraphyses filiform [thread-like], enlarged at tips; conidia 18-25 x 5-6 microns, "formed on erumpent acervuli, 1-septate and constricted at the septum"