Divisi
Powdery mildew
· Fungal
Photo: Dmitry Brant · CC BY-SA 4.0
Powdery mildew is a group of fungi that live on the surface of the leaf, pushing tiny feeding roots into the skin of the leaf while their dry, flour-like spores blow to the next plant on the wind. Unlike most leaf diseases it does NOT need rain or wet leaves — it only needs humid air, so it strikes in warm, dry weather. On smallholder plots it commonly hits cucurbits (pumpkin, cucumber, melon, squash), tomato, pepper, common bean, mango and grape.
Schlaghecken Josef · CC BY-SA 4.0 
M.E. Bartolo, Bugwood.org · CC BY 3.0
Why it matters
Powdery mildew coats the leaves so the plant can no longer feed itself from the sun — in a bad attack it can cost you as much as 40% of your harvest, and it robs fruit of sweetness and size while leaving them open to sunscald once the leaves die back. It matters most because it moves fast: the dry spores blow from leaf to leaf on the wind and can blanket a whole plant in a week or two. Once the white powder has spread across the canopy the fungus is buried in the leaf and hard to knock back — sprays can stop it climbing further but they cannot un-white the leaves it has already killed. That is why you win or lose this fight in the first few days, at the very first patches.
When to act
First white powdery colonies on lower or shaded leaves; begin protectant sprays before it spreads over the canopy
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 powdery mildew field guide
- Identify it
- Scout for it
- Control it
15 field-guide sections in the app
The full guide to powdery mildew — 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 powdery mildew?
The first thing you see: small, round white-to-grey powdery patches, like someone dusted the leaf with flour or wood ash. Rub one with your finger and the powder smudges off — that is the giveaway. They show up first on older, lower and shaded leaves, usually on the top side, but on some crops (pepper, tomato) look on the underside too.
When should I take action against powdery mildew?
First white powdery colonies on lower or shaded leaves; begin protectant sprays before it spreads over the canopy
How do I control powdery mildew?
Prevent it first (best value): give every plant room to breathe — space plants wider and prune out crowded inner growth so air moves through and dries the humid pockets the fungus needs. Go easy on nitrogen fertiliser: too much makes soft, leafy growth that mildew loves. Keep the plot in more sun, less shade.
Which crops does powdery mildew affect?
Among the crops covered here: Common bean, Mango, Tomato.
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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