Numbered Publications by Stanton, Michele Publications by Michele Stanton PPFS-FR-S-3: Blackberry Rosette (Double Blossom) Michele Stanton, Nicole Gauthier | Dec. 1, 2017 (Major Revision) Rosette disease, caused by the fungus Cercosporella rubi, is a serious and destructive disease of blackberries in most parts of Kentucky. In some locations, growers have been forced out of growing blackberries because of rosette disease.