Divisi
Boll rot
Diplodia gossypina · Fungal
Photo: Scot Nelson · CC0
Boll rot is not one germ but a team of opportunist fungi and bacteria (led by Diplodia gossypina) that invade the cotton boll through insect wounds, growth cracks and natural openings. It needs the boll to stay wet: warm, humid, rainy weather and a dense, poorly-aired canopy keep bolls damp long enough for the rots to take hold and spoil the fibre inside.
Scot Nelson · CC0 
Scot Nelson from USA · CC0
Why it matters
Boll rot spoils the cotton fibre inside the boll (the pod you actually pick and sell) — so you lose the finished product, not just some leaves. In a warm, wet season it can rot up to half your crop (50%), and it strikes late, after you've already spent months and money growing those bolls. Once the fungus is inside a boll, that boll is finished — no spray brings it back, and in a dense, damp canopy it jumps from boll to boll fast. Because a direct fungicide rarely pays on cotton, beating boll rot is about prevention — keeping bolls dry and free of insect wounds — not rescue.
When to act
Act when developing bolls in the lower, dense canopy start to rot during wet weather, especially where bollworm or sucking-bug damage has opened wounds.
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 boll rot field guide
- Identify it
- Scout for it
- Control it
16 field-guide sections in the app
The full guide to boll 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 boll rot?
The first sign: on a green, developing boll you'll see a small water-soaked spot — a dark, wet, greasy-looking patch that feels soft, not firm like healthy boll wall. It often sits right beside an insect sting or hole, or low down where a shaded boll stays damp after rain.
When should I take action against boll rot?
Act when developing bolls in the lower, dense canopy start to rot during wet weather, especially where bollworm or sucking-bug damage has opened wounds.
How do I control boll rot?
Prevent it — open up the canopy so bolls dry fast (your strongest tool). Give plants correct, not-too-tight spacing, and go easy on nitrogen fertiliser: too much makes soft, leafy 'rank' growth (thick, lush growth) that traps damp, still air around the bolls. Sun and moving air dry bolls quickly and starve the rot of the wetness it needs.
Which crops does boll rot affect?
Among the crops covered here: Cotton.
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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