During the study of alternative weed hosts for Cercospora beticola Sacc., a causal agent of cercospora leaf spot of sugar beet in Northern Iran, a species of the genus Microcyclospora J. Frank et al. was isolated from Rumex crispus showing leaf spot symptoms in the Talesh region (Guilan province). Microcyclospora, with M. pomicola J. Frank et al. designated as type species, was recently segregated from Pseudocercospora Speg. s. str. based on phylogenetic and morphological differences (Frank et al. 2010). Currently the three species known in Microcyclospora are associated with sooty blotch and flyspeck (SBFS) blemishes on the surfaces of pomaceous fruits, specifically apples (Colby 1920; Frank et al. 2010). Here we describe a new Microcyclospora species from leaf spots on Rumex crispus that differs morphologically from the three other known species of the genus.
