Although club root and black rot are the most important diseases of the cabbage, the following cause more or less trouble: Leaf-spot (Sphaerella brassicaecola); stem canker and drop (Phoma oleracea) ; mildew (Peronospora parasitica); a dark rot (Sclotinia libertiana), studied by the Missouri Botanical Garden ; a bacterial soft rot closely related to Bacillus carotovorus; root rot or stem rot (Corticium vagum); and white rust (Cystopus candidus).