Divisi
Downy mildew
Peronosporaceae · Fungal
Photo: blastcat (iNaturalist) · CC BY 4.0
Downy mildew is a family of fungus-like water moulds (oomycetes) that attack the leaves of many crops — cucumber, pumpkin and other vegetables, onion, cabbage, sorghum and grape. Its spores need a film of water to grow, so cool nights, heavy dew, fog, rain and high humidity drive fast, leaf-killing outbreaks. Some kinds blow in on the wind from far away each season, arriving before you ever see them.
Jochen Kreiselmaier, DLR-Rheinpfalz · CC BY 4.0 
Jerzy Opioła · CC BY-SA 4.0
Why it matters
Downy mildew rots the leaves that feed your crop, and once it takes hold in cool, wet weather it can spread across a whole field in days and cost you up to 60% of your harvest. It is hard to stop once it is established because by the time you see the fuzzy growth underneath a leaf, the spores have already blown onto dozens of other leaves, and a leaf that has browned and died will never recover. The only reliable win is to prevent it and catch the very first spots — chasing it after it is everywhere rarely works.
When to act
Begin protectant sprays when cool humid weather with leaf wetness sets in, or at the first angular leaf lesions.
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 downy mildew field guide
- Identify it
- Scout for it
- Control it
19 field-guide sections in the app
The full guide to downy 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 downy mildew?
The first sign you see: pale yellow patches on the TOP of the leaf. On many crops the patches are angular — blocky, squared-off little tiles, because the leaf veins fence them in (this 'boxed-in' shape is the giveaway). On onion and sorghum they show as long pale streaks running along the leaf.
When should I take action against downy mildew?
Begin protectant sprays when cool humid weather with leaf wetness sets in, or at the first angular leaf lesions.
How do I control downy mildew?
Prevent it first — plant resistant varieties (your strongest tool): where you can get them, grow downy-mildew-resistant or tolerant varieties bred for your crop and area. This is the single most effective non-chemical step and cuts the disease before it starts.
Which crops does downy mildew affect?
Among the crops covered here: Cabbage, Cucumber, Onion, Sorghum.
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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