Septocyta ruborum is a species of fungus in the Ascomycota.[1] Its taxonomic relationship to other taxa in the Ascomycota is unknown, and it has not been assigned with certainty to any order or family (incertae sedis). It is a plant pathogen and grows on Rubus laciniatus, R. nessensis, R. procerus and wild blackberry (R. fruticosus); it causes purple blotch or stem spot disease, also known as dieback of blackberries.