Divisi
Rust
· Fungal
Photo: James Kolmer · Public domain
Rust is a wind-borne fungal disease that erupts as powdery, rust-coloured pustules on the leaves and stems of wheat, maize, beans, groundnut, sorghum and sunflower. It thrives in cool, mild weather with heavy dew and damp air, spreads fast on wind and splashing rain, and slowly drains the plant by shutting down the green leaf that fills the grain.
USDA · Public domain 
Clemson University - USDA Cooperative Extension Slide Series, Bugwood.org · CC BY 3.0 us
Why it matters
Rust is a quiet thief. Once it takes hold it can rob you of up to 60% of your harvest — grain that comes out small and shrivelled because the leaves died before they could feed it. It matters most because it spreads on the wind from field to field and, once the pustules are everywhere, no spray can bring back a leaf that is already dead. The only way to win is to stop it early or keep it out from the start.
When to act
first rust pustules appearing on lower leaves, especially before or during flowering
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 rust field guide
- Identify it
- Scout for it
- Control it
13 field-guide sections in the app
The full guide to rust — 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 rust?
What you see first: small raised bumps (pustules) that break open like tiny blisters and dust your finger with powder when you rub the leaf — the powder is orange, brown, reddish or yellow, the exact colour of rust on old iron.
When should I take action against rust?
first rust pustules appearing on lower leaves, especially before or during flowering
How do I control rust?
Prevent it first — resistant varieties (your strongest, cheapest shield): plant a rust-resistant variety suited to your area whenever you can. This is the single most effective control — it stops most of the disease before it starts, with no spraying and no cost each season.
Which crops does rust affect?
Among the crops covered here: Bambara groundnut, Garlic, Groundnut, Lablab, Maize, Sorghum, Sunflower, Wheat.
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.
Check what grows on your farm