Divisi
Tuber rots
· Fungal
Photo: Scot Nelson · CC0
Tuber rots are a group of soft and dry rots caused by soil and wound fungi (and often bacteria) that get into potato, yam, cassava and sweet-potato tubers through harvest bruises, insect or nematode holes, or thin, unset skins. They do their worst damage late in the season and in the store, spreading tuber-to-tuber fastest in warm, damp, stuffy heaps.
Why it matters
Tuber rots turn a harvest you already grew and dug into a smelly, leaking mess — a bad rot can destroy up to 60% of your tubers, sometimes after they look fine going into store. It hurts most because it strikes at the end, when all the season's work is already spent, and it is hard to stop once it starts: one rotten tuber quietly infects the ones touching it, so a small patch can rot out a whole heap while it sits in the dark. You often only find out when you open the store to sell or eat, and by then the loss is done.
When to act
Rot found in stored or field tubers, or wounding during a wet harvest window; discard and cure remaining tubers 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 tuber rots field guide
- Identify it
- Scout for it
- Control it
15 field-guide sections in the app
The full guide to tuber rots — 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 tuber rots?
The first sign is a soft or sunken patch on the tuber skin, usually starting at a bruise, a cut, or an insect hole. The patch is brown to black, and when you press it with your thumb it feels soft and gives way instead of staying firm like healthy flesh.
When should I take action against tuber rots?
Rot found in stored or field tubers, or wounding during a wet harvest window; discard and cure remaining tubers immediately.
How do I control tuber rots?
Prevent it first — this is where you win. Harvest at full maturity in dry weather, when the skin is firm and set (rub it — a mature skin does not slip off). Handle tubers gently: lift, don't throw or tip them, so you make no fresh bruises or cuts for the fungi to enter. Only ever store clean, whole, undamaged tubers.
Which crops does tuber rots affect?
Among the crops covered here: Cassava, Sweet potato, Yam.
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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