Ringspot (Black blight)—Mycosphaerella brassiciola
In California, ringspot occurs only on brussels sprouts. Symptoms consist of circular leafspots (0.5
inch in diameter) that range from light brown to black in color. With time these spots develop concentric
rings much like a target pattern. Small spherical
fruiting structures may also be observed within the leafspots. If the disease is severe, some defoliation
may take place. This pathogen may also cause dark lesions to appear on outer leaves.
Ringspot is favored by cool, moist conditions.
Spores produced by this pathogen are spread primarily by
wind. It can also be carried on seed. Remove diseased plants
and destroy all plant residue. Weed out volunteers. Plant
clean seed or disease-free transplants.
symptoms on brussels sprouts
up of circular leafspot