M. rosae produces black spots of about two to 12 mm in
diameter usually in the upper surface of the leaves (Fig.1a). Often, those spots may have irregular, radiate, feathery borders (Fig. 1b). In older lesions, black spore-bearing
structures, called acervuli, can be observed as well as white,slimy masses of conidia (Fig. 2a). Yellowing around the lesions on infected leaves can occur, and severe defoliation occurs in the most susceptible cultivars. While leaves are the most susceptible part of the plant, stipules and pedicels can also be infected. Spots can also be found also in peduncles, fruits and sepals. Symptoms of black spot are
usually confused with those of Cercospora leaf spot (See EDIS publicationCercospora Leaf Spot of Rose at http://edis.ifas.ufl.edu/PP267).