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How to Manage Pests

Pests in Gardens and Landscapes

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.

Solutions

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.

Ring spot symptoms on brussels sprouts
Ringspot symptoms on brussels sprouts

Close up of circular leafspot
Close up of circular leafspot

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