Symptoms develop during storage usually after a period of 6 – 10 weeks. The bulb scales soften around the neck giving rise to a brown sunken lesion. The rot spreads throughout the rest of the bulb followed by the presence of the typical Botrytis grey mould with small black fruiting bodies and prolific grey spore masses.
Most infection is seed-borne or from sets. Spores from contaminated seed produce mycelia which invade seedlings as they emerge although symptoms are not visible until after harvest. Once established can be further spread by wind-borne spores which enter plants via wounds or damaged tissue. Can survive in the soil as sclerotia or on crop debris.
Cool, wet weather.
This is a common and widespread disease of stored onions and shallots. Yield losses of up to 30 % have been recorded.
Find out more information on the key disease threats to your onion and leek 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.