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Onion Neck Rot


Onion Neck Rot

Usually appear in


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Caused By:-     Botrytis Species


There are at least seven Botrytis species that affects Onion and other Allium species Three species B. allii, B. squamosa and B. cinerea causes neck rot, but the most serious of these species causing neck rot is B. allii. THE Onions appear healthy when growing, but start to show symptoms of the disease after 4-8 weeks of storage. The top of the bulb is soft when pressed, with brownish-black discolouration under the dry, outer scales.
This major disease of onion is especially caused by not allowing the bulbs to dry properly before harvesting. In general, white varieties are especially susceptible, but red and yellow varieties may also be attacked.
The fungus often enters bulbs through the neck when tops are damaged before they have dried adequately. After infection, the fungus grows down through the inner scales and may partly rot the bulb before any damage shows on the outside. This disease is also seed-borne.
In severe cases the bulbs may decay completely and be covered with fluffy, grey mould. The sides and base of bulbs are rarely attacked. Infection does not appear to spread between bulbs in store.
Picture by Howard F. Schwartz, Colorado State University,
See these other Grey Moulds and Botrytis fungi Bean Chocolate Spot, Botrytis, Grey Mould, Lettuce Grey Mould, Lily Disease, Peony Wilt, Rose Grey Mould, Snowdrop Grey Mould, Strawberry Grey Mould.


Fungicide applications during the season and especially prior to harvest may reduce the incidence of neck rot.
This fungi survive the winter on previously infected onion debris in the soil which are sources of the fungi the following season. Therefore good husbandry is essential if you are to avoid this pest. This includes crop rotation if possible.
Allow tops to mature well before harvest.
High nitrogen fertiliser after summer growth causes soft tissue growth which is more easily attacked.
Use fungicide treated seed and or seed from a reputable source.
Store in well-ventilated area above freezing temperature.
Grow varieties that are known to be resistant or store well.

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