A previously unrecorded black mildew was observed on foliage of Mitracarpus hirtus (Rubiaceae) in Ouro Preto, state of Minas Gerais (Brazil). Meliola psychotriae (Ascomycetes) was associated with the black mildew. This is the first record of this pathogen on M. hirtus and the ninth record of a fungal pathogen on this host worldwide. Although representing a contribution to the knowledge of the mycobiota of this weed, M. psychotriae is regarded as having no potential for biological control because damage to the host is minimal.