Divisi
Collar rot
Sclerotium rolfsii · Fungal
Photo: Edward L. Barnard - Florida Department of Agriculture and Consumer Services · CC BY 3.0 us
Collar rot is a soil-borne fungal disease (Sclerotium rolfsii) that attacks the stem base — the 'collar' — of seedlings and young plants right at the soil line. It grows out of old crop residue lying on warm, moist soil, wrapping the stem in a white cottony mould that rings and chokes it until the plant wilts and dies. It survives between crops as tiny hard beads (sclerotia) that last for years in the soil, and it strikes a wide range of smallholder crops including groundnut, beans, tomato, chickpea and soybean.
Glenn Teves (Molokai) · CC0 
Lindsey D. Thiessen, Jason E. Woodward · CC BY 4.0
Why it matters
Collar rot rings the stem right at the soil line and chokes the plant, so a healthy young groundnut, bean or tomato can wilt and die in just a few days — and a bad outbreak can cost you up to 40%, nearly half your crop. The cruel part is that a plant already choked (girdled) at the collar is dead: no medicine brings it back, so you can only save the plants around it. And once it takes hold it leaves behind thousands of tiny hard 'seeds' (sclerotia) that survive in your soil for years, ready to attack your next crop — which is why it is so hard to be rid of once it is established.
When to act
Scattered seedlings or young plants wilting and collapsing at the soil line, especially in warm wet patches with residue.
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 collar rot field guide
- Identify it
- Scout for it
- Control it
17 field-guide sections in the app
The full guide to collar 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 collar rot?
The first thing you see: a healthy young plant — groundnut, beans, tomato, chickpea or soybean — suddenly wilts, yellows and flops over as if it is dying of thirst, usually one plant here and there in the warm, wet, shaded patches. But the soil is moist and watering does not revive it, while the plants right next to it stay green.
When should I take action against collar rot?
Scattered seedlings or young plants wilting and collapsing at the soil line, especially in warm wet patches with residue.
How do I control collar rot?
Prevent it first — starve the fungus with rotation (your strongest tool). The rot feeds on groundnut, beans, tomato, chickpea and soybean. Plant a cereal — maize, sorghum or millet — on that land for 2-3 seasons; with no host to feed on, the fungus in the soil slowly dies down. Never plant one susceptible crop straight after another on land that has rotted.
Which crops does collar rot affect?
Among the crops covered here: Chickpea, Groundnut, Soybean, 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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