Neck Rot - Onions
Botrytis alli (and other spp)
Pathogen
Fungus
Hosts
Onions
Symptoms
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.
Development
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.
Favourable Factors
Cool, wet weather
Importance
This is a common and widespread disease of stored onions and shallots. Yield losses of up to 30 % have been recorded.
Control
Fungicide treated seed or sets
Dry bulbs soon after harvest
Removal of crop debris
Rotation of at least 3 years
Suitable storage conditions
