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Sclerotinia head rot
Sclerotinia sclerotiorum · Fungal
Photo: Jymm · Public domain
Sclerotinia head rot is a fungal rot of the sunflower head caused by Sclerotinia sclerotiorum. Tiny airborne spores land on the ageing flowers at the front of the head and grow back through it. The fungus softens and bleaches the head, packs it with white cottony mould, and leaves behind hard black lumps (called sclerotia) that drop into the soil and wait there for years. It thrives in cool, wet, humid weather during and after flowering.
Why it matters
This is the most damaging rot of sunflower once it takes hold. In a cool, wet season it can rot so many heads that you lose up to 70% of your crop — the head simply falls apart and the seed spills or goes mouldy before you can harvest. It is hard to beat because by the time you see it the fungus is already deep inside the head, there is no reliable spray to cure it, and every rotten head drops hard black lumps into your soil that can start the disease again years later.
When to act
first bleached, soft lesions on the back of heads during flowering to grain fill under wet weather
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 sclerotinia head rot field guide
- Identify it
- Scout for it
- Control it
15 field-guide sections in the app
The full guide to sclerotinia head 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 sclerotinia head rot?
The first sign is a soft, pale, water-soaked patch on the BACK of the head (the side facing the ground), usually appearing after flowering. It looks bleached, like a wet bruise, and spreads outward day by day until much of the head goes a light straw or bone colour.
When should I take action against sclerotinia head rot?
first bleached, soft lesions on the back of heads during flowering to grain fill under wet weather
How do I control sclerotinia head rot?
Prevent first — rotate (your strongest tool): the black lumps live in the soil for years, so rotate with cereals (maize, sorghum, millet, wheat) for several years before returning sunflower to a field. Do not follow sunflower with other broadleaf hosts such as beans, soya, groundnut or cabbage, which feed the same fungus.
Which crops does sclerotinia head rot affect?
Among the crops covered here: Sunflower.
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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