Divisi
Coffee leaf rust
Hemileia vastatrix · Fungal
Photo: Howard F. Schwartz · CC BY 3.0 us
Coffee leaf rust, caused by the fungus Hemileia vastatrix, is the most damaging disease of coffee worldwide. It infects the underside of the leaves: spores need a film of water (rain or dew) to germinate and slip in through the tiny leaf pores, then throw up orange, powdery spore masses that spread on wind, rain splash, and on the hands, clothes and animals that move through wet bushes. Heavy infection strips the bush of its leaves, so it cannot fill this year's cherries or build next year's crop.
Daniel Case · CC BY-SA 4.0 
Carvalho et al. · CC BY 2.5
Why it matters
Coffee leaf rust is the most serious disease your coffee will face. It attacks the leaves and makes the bush drop them, and a bush with no leaves cannot fill its cherries this year or carry a good crop next year — a heavy outbreak can take up to 70% of your harvest. The hard part is that once the leaves are covered in orange spots and falling, no spray can bring them back — copper only shields the leaves that are still healthy. So everything depends on spotting the very first spots and acting before it spreads through the bush.
When to act
First yellow-orange powdery spots on lower leaves, especially on heavily bearing bushes going into the rains.
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 coffee leaf rust field guide
- Identify it
- Scout for it
- Control it
14 field-guide sections in the app
The full guide to coffee leaf 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 coffee leaf rust?
First sign: on the older, lower leaves you'll see small pale-yellow, oily-looking spots, round like little coins. Hold the leaf up to the light and each spot looks see-through, like a small window in the leaf.
When should I take action against coffee leaf rust?
First yellow-orange powdery spots on lower leaves, especially on heavily bearing bushes going into the rains.
How do I control coffee leaf rust?
Prevent — plant resistant bushes (your strongest tool): where you can choose new plants or replant, grow rust-resistant coffee varieties (such as the catimor / sarchimor types, Ruiru 11 or Batian, where they suit your area). A resistant bush shrugs off most attacks with no spraying at all — this is the cheapest, longest-lasting protection you have, which is why it beats every spray.
Which crops does coffee leaf rust affect?
Among the crops covered here: Arabica coffee, Robusta coffee.
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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