Divisi
Angular leaf spot
Pseudocercospora griseola · Fungal
Angular leaf spot is a fungal disease of common beans (caused by Pseudocercospora griseola). It is named for the angular, block-shaped spots it makes on the leaves: the fungus gets trapped between the tiny leaf veins, so each spot has straight sides instead of being round. It spreads by wind and by rain splashing spores up from the soil and lower leaves, and it thrives in cool-to-warm, very humid weather — roughly 16–28°C with damp, still air in a crowded bean canopy.
Meswaet Y, Mangelsdorff R, Yorou NS, Piepenbring M (2021) Unravelling unexplored diversity of cercosporoid fungi (Mycosphaerellaceae, Mycosphaerellales, Ascomycota) in tropical Africa. MycoKeys 81: 69-138. https://doi.org/10.3897/mycokeys.81.67850 · CC BY 4.0 
Rasbak · CC BY-SA 3.0
Why it matters
In a wet season angular leaf spot can cost you up to 70% of your bean harvest. The spots kill the leaves, and without healthy leaves the plant cannot fill its pods, so you are left with few, small, poorly-filled beans. It is hard to beat once it takes hold, because the fungus rides in on the seed and survives on old bean trash in the soil, so it comes back season after season on the same land. And a spray can only protect healthy leaves — it cannot heal a spot that has already formed — so the whole game is catching it early and staying ahead of it.
When to act
Protect the crop when the first angular grey-brown spots appear on lower leaves, especially from flowering onward in humid 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 angular leaf spot field guide
- Identify it
- Scout for it
- Control it
15 field-guide sections in the app
The full guide to angular leaf spot — 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 angular leaf spot?
The first thing you see: small angular, block-shaped spots on the lower, older leaves. They have straight sides — like little tiles, or a cracked-mud pattern — because each spot is boxed in by the tiny leaf veins. That straight-sided, angular shape is the giveaway: most other bean leaf diseases make round spots.
When should I take action against angular leaf spot?
Protect the crop when the first angular grey-brown spots appear on lower leaves, especially from flowering onward in humid weather.
How do I control angular leaf spot?
Prevent it — start with the variety. Plant a tolerant or resistant bean variety suited to your area (ask your extension officer or agro-dealer which local varieties hold up to angular leaf spot). This is your strongest defence that does not need a spray, and it costs you nothing extra at planting.
Which crops does angular leaf spot affect?
Among the crops covered here: Common bean.
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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