Divisi
Brown spot
Cochliobolus miyabeanus · Fungal
Photo: Donald Groth, Louisiana State University AgCenter · CC BY 3.0 us
Brown spot (Cochliobolus miyabeanus) is a seed- and soil-borne fungal disease of rice that thrives on starved, drought-stressed soil. It scatters small, sesame-seed-shaped brown spots across the leaves, blights seedlings in the nursery, and spots the grain at harvest. Because it rides on infected seed, survives in old rice straw, and blows about on wind-carried spores (the fungus's tiny dust-like seeds), it comes back season after season on hungry soil (low nitrogen, potassium and silicon) until the fertility is corrected.
GarryMann · Public domain 
William M. Brown Jr., Bugwood.org · CC BY 3.0 us
Why it matters
Brown spot is a disease of hungry, thirsty soil, and on starved land it can be brutal: in a bad year it can take nearly half your rice crop (up to 45%), killing seedlings in the nursery and spotting the grain so it won't sell or store. It is hard to beat once it takes hold, because the fungus lives on inside your seed and in old rice straw and blows in on the wind, coming back every single season. No spray truly cures it, either: the real fix is feeding and watering the soil properly, so a farmer who only sprays keeps losing. This is the disease behind the great Bengal famine, so on poor land it is worth taking seriously.
When to act
spots on seedlings or spreading lesions on leaves in nutrient-poor patches
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 brown spot field guide
- Identify it
- Scout for it
- Control it
17 field-guide sections in the app
The full guide to brown 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 brown spot?
The spots (easiest to recognise): many small, brown, oval spots scattered evenly all over the leaf, each about the size and shape of a sesame seed. Young spots are tiny, round and dark reddish-brown; older ones grow into ovals with a grey or straw-coloured centre and a brown edge, sometimes ringed by a faint yellow halo. On a badly hit leaf, dozens of these even-sized spots pepper the whole blade.
When should I take action against brown spot?
spots on seedlings or spreading lesions on leaves in nutrient-poor patches
How do I control brown spot?
Prevent it first: feed and water the soil (the single most important control). Brown spot is really a hunger disease. Correct the soil with balanced nitrogen and potassium, and add silicon where the land is worn out; then keep the paddy evenly watered and never let it dry out and drought-stress the crop. Well-fed, well-watered rice shrugs the disease off, and no other step comes close to this one.
Which crops does brown spot affect?
Among the crops covered here: Rice.
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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