Divisi
Damping-off
Pythium spp. · Fungal
Photo: Gerhard Bedlan (Institut für Pflanzenschutz, BOKU, Tulln, Austria) · CC BY-SA 4.0
Damping-off is a seed and seedling rot caused by soil-borne fungi and water-moulds (Pythium and its relatives) that live in cool, wet, poorly drained nursery soil. It strikes only the youngest plants: it can rot the seed before it ever comes up (pre-emergence) or rot the stem right at the soil line so the standing seedling suddenly topples over (post-emergence). It is a nursery and seedbed disease of tomato, cabbage, onion, beans, tobacco and other vegetable seedlings.
Gerhard Bedlan (Institut für Pflanzenschutz, BOKU, Tulln, Austria) · CC BY-SA 4.0 
Dr. Jan Hinrichs-Berger, Landwirtschaftliches Technologiezentrum Augustenberg · CC BY 3.0
Why it matters
Damping-off hits your crop at its most helpless moment — the seedbed — and a bad outbreak can wipe out up to 80% of your seedlings before they ever reach the field. It spreads fast through a wet, crowded nursery, jumping from one seedling to the next along the damp soil, so a healthy-looking tray can be half-empty in two or three days. Once the little stems have rotted through there is no cure and no bringing them back: you can only stop it reaching the plants that are still standing. That is why everything here is about preventing it and catching the very first collapsed patch.
When to act
Act preventively; once seedlings collapse in a patch, reduce watering and remove affected trays or seedbed sections immediately.
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 damping-off field guide
- Identify it
- Scout for it
- Control it
15 field-guide sections in the app
The full guide to damping-off — 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 damping-off?
The first thing you see is gaps. Patchy, thin emergence — seed that never comes up, or bare blank spots in a tray or seedbed where the rest of the row came up fine. That missing seed has already rotted underground before breaking the surface.
When should I take action against damping-off?
Act preventively; once seedlings collapse in a patch, reduce watering and remove affected trays or seedbed sections immediately.
How do I control damping-off?
Prevent it first — this is your strongest tool (cultural control works best on this disease). Sow thinly so seedlings aren't crowded, in raised, well-drained beds or clean sterile media (fresh potting mix or well-cured compost, not old garden soil). Don't sow too deep. Start with clean or treated seed.
Which crops does damping-off affect?
Among the crops covered here: Cabbage, Niger seed (noug), Onion, Tobacco, Tomato.
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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