How to Manage Pests
UC Pest Management Guidelines
In California, this disease occurs primarily on Brussels sprouts. Symptoms consist of circular leafspots (0.5 inch in diameter) that range in color from light brown to black. With time these spots develop concentric rings much like a target pattern. Small spherical fruiting structures may also be observed within the leafspots. If disease is severe, some defoliation may take place. 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 a protectant fungicide before infection takes place.
UC IPM Pest Management Guidelines: Cole Crops