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.
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.
Cool, wet weather.
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.
Find out more information on the key disease threats to your field brassica crop. For each disease you will find out the importance of the disease in terms of potential yield penalty, how to identify the disease in its early stages and our advice on the best control strategies.