Ringspot
Mycospharella brassicicola
Pathogen
Fungus
Hosts
Field brassicas
Symptoms
Rounded, dark brown sunken lesions up to 20 mm in diameter. Unlike Alternaria, (dark leaf spot), these lesions do not grow across major leaf veins.
The lesions have well defined edges with yellow margins around the edge. Within the lesions are dark concentric rings of black fruiting bodies. Under severe disease pressure the lesions can coalesce to the extent that whole leaves, or even entire plants, are totally devoid of any remaining healthy green leaf tissue.
Development
Requires periods of cool, damp conditions for the fungus to establish. Spores are wind spread and ringspot overwinters on crop debris or suitable weed hosts.
Infected seed can also be a source of infection.
Favourable Factors
Cool, wet weather
Importance
An important economic disease of brassicas which can infect many members of the brassica family, especially in intensive vegetable growing regions.
Ringspot can be directly responsible for significant economic loss by adversely affecting crop quality, particularly on the buttons of Brussels sprouts.
Control
Clean seed
Removal of host weeds and crop debris
Rotation
Fungicides programmes should be started at the first sign of infection
