Divisi
Botrytis neck rot
Botrytis allii · Fungal
Photo: Lester E. Dickens, Bugwood.org · CC BY 3.0
Botrytis neck rot is a fungal storage rot of onions caused by Botrytis allii. It slips in through the neck and any wound late in the season, usually with no sign at all, then stays hidden through drying until the bulbs are in store — where it softens the neck, grows a grey mould, and rots the bulb from the top down. Because the damage only shows weeks after harvest, this disease is beaten in the field and the drying shed, not in the store.
Jochen Kreiselmaier, DLR Rheinpfalz · CC BY-SA 4.0 
Jerzy Opioła · CC BY-SA 4.0
Why it matters
Neck rot is the onion grower's storage heartbreak. A store that looked perfect at lifting can lose up to half of its bulbs (50%) to a soft grey rot weeks later — after you have already spent the whole season, and the money, to grow, lift and store them. The fungus creeps in silently through the neck as the crop dries down and shows nothing until it is rotting in the bag, and by then no spray can save that batch. That is why everything rides on getting the crop fully mature, well dried, and gently handled before it ever reaches the store — once it is rotting, the loss is already made.
When to act
Manage before harvest and in store; the rot shows up weeks into storage, so prevention at maturity and curing is the decision point.
This guidance is general, compiled from published agronomic references including FAO and CABI. Thresholds and timing shift with your crop, your variety and the season.
In much of the region a spray is simply called mushonga — medicine. But a chemical group you cannot name is one you cannot rotate, and a product you did not write down has no pre-harvest interval you can observe. Mushonga, and other farming words →
The full botrytis neck rot field guide
- Identify it
- Scout for it
- Control it
15 field-guide sections in the app
The full guide to botrytis neck rot — every symptom to check, how and when to walk your field looking for it, and the controls that actually work, ranked. Built into your crop plan, so you are told to look before it costs you a harvest.
Crops it affects
Frequently asked questions
How do I identify botrytis neck rot?
The first sign (in store): weeks after harvest, a bulb that felt firm starts to soften at the neck — the top of the bulb, where the green leaves used to join. Press it and it gives; the tissue just under the skin looks water-soaked and 'cooked', a pale tan-brown, and often sunken. The softening always starts at the top and works downward — that is why it is called neck rot.
When should I take action against botrytis neck rot?
Manage before harvest and in store; the rot shows up weeks into storage, so prevention at maturity and curing is the decision point.
How do I control botrytis neck rot?
Prevent it — mature and cure (your strongest tool): let the tops fall and the crop fully mature before lifting, so the neck closes and starts to dry. Then cure thoroughly — meaning dry the onions in a single layer in a warm, airy, shaded place (or a well-ventilated shed) until the necks are papery, tight and rustling dry. A dry, sealed neck shuts the very door the fungus enters by. And cap late-season nitrogen fertiliser — too much makes thick, soft, sappy necks that never dry properly.
Which crops does botrytis neck rot affect?
Among the crops covered here: Garlic, Onion.
Catch it before it costs you a harvest
Divisi builds scouting into your crop plan — it tells you when to walk your field, what to look for at that stage, and what to do when you find it. Free for farmers, works offline.
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