Divisi
Carrot leaf blight
Cercospora carotae · Fungal
Carrot leaf blight is a fungus (Cercospora carotae) that attacks the leaves and leaf-stalks of carrots, not the root itself. It is one of the two common carrot leaf blights — the other is Alternaria — and it favours warm, damp weather. Its spores blow and splash from spotted leaves and old carrot debris onto healthy plants, and in a wet spell they can spot and brown the whole top of the crop. Because the leaves are the engine that fills the root, losing them means small, poorly-coloured carrots and tops too weak to grip when you lift.
Why it matters
The carrot's leaves are the engine that feeds the swelling root — so a disease that scorches the tops steals the crop straight from the ground. A bad leaf blight can strip the tops and cost you up to 4 in every 10 carrots (40% of your crop): the roots stay small, pale and poorly flavoured because the leaves died before they could fill them. It spreads fastest in warm, damp weather, jumping plant to plant on splashing rain and dew, and it comes back year after year from infected seed and old carrot leaves left in the soil. Worst of all, weakened, rotted-off tops snap when you try to pull the roots, leaving carrots stuck in the ground at harvest.
When to act
first leaf spots found — about 1 in 10 plants showing spots — or warm, wet, humid weather with long dew forecast; start protectant fungicide early, before the spots multiply
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 carrot leaf blight field guide
- Identify it
- Scout for it
- Control it
15 field-guide sections in the app
The full guide to carrot leaf blight — 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 carrot leaf blight?
The first thing you see: small grey-tan to brown spots scattered on the leaves, each ringed by a darker border and often a thin yellow edge. They are small — about 2–3 mm, the size of a pinhead — round to angular, and they start on the younger inner leaves and the leaf-stalks first.
When should I take action against carrot leaf blight?
first leaf spots found — about 1 in 10 plants showing spots — or warm, wet, humid weather with long dew forecast; start protectant fungicide early, before the spots multiply
How do I control carrot leaf blight?
Prevent it first — start clean (your strongest tool): the fungus rides in on the seed itself and on old carrot leaves left in the soil, so use fresh, certified disease-free seed every time, and rotate at least 3 years off the carrot family (no carrot, parsnip, celery, parsley or coriander on that ground) so last year's spores starve out. Where you can find one, plant a leaf-blight-tolerant variety. Starting clean is worth far more than any spray later.
Which crops does carrot leaf blight affect?
Among the crops covered here: Carrot.
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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