This pathogen may also infect the sprouts, causing dark lesions on outer leaves. The infection and disease development are favored by cool, moist conditions. Spores produced by this pathogen are spread by wind. Mycosphaerella brassicicola will persist in soil on infected plant residues only. There is some evidence that this pathogen may be carried on seed.
Incorporate plant residues so that infected material decomposes fully.
Remove volunteer plants that may be infected. Plant disease-free transplants. If ringspot is a problem in the area, use protectant fungicides before infection takes place. Do not apply within this many days of harvest. The Regents of the University of California.