Divisi
Phytophthora blight
Phytophthora capsici · Fungal
Photo: Kerstin Mahler, Anbauberatung Gemüsebau sowie Heil- und Gewürzpflanzen, beim DLR Rheinpfalz in Neustadt/Wstr. · CC BY-SA 4.0
Phytophthora blight is a water mould (an oomycete — a fungus-like organism that swims and spreads in water) that lives in wet soil. It makes swimming spores in waterlogged ground and rides splashing rain and runoff from plant to plant, rotting the roots, the stem base (crown), the leaves and the fruit of peppers, chillies, tomatoes, eggplants and cucurbits (pumpkins, cucumbers, melons, squash). It thrives in warm, wet weather and can move through a whole bed in days.
Kerstin Mahler, Anbauberatung Gemüsebau sowie Heil- und Gewürzpflanzen, beim DLR Rheinpfalz in Neustadt/Wstr. · CC BY-SA 4.0 
Kerstin Mahler, Anbauberatung Gemüsebau sowie Heil- und Gewürzpflanzen, beim DLR Rheinpfalz in Neustadt/Wstr. · CC BY-SA 4.0
Why it matters
Once this water mould gets into a wet field it can take your entire crop — up to 100% — because it kills the plant at the roots and stem base where you cannot see it, and no spray brings a dead plant back. It spreads fastest exactly when you most want to water: warm days and soaked soil let the spores swim from one plant to the next in hours. That is why it is so hard to beat once it starts — you cannot cure infected plants, you can only stop it reaching the healthy ones, so everything depends on drainage and catching the very first sick plant.
When to act
First wilting or stem lesions after heavy rain or irrigation; act immediately on drainage and remove affected plants (spreads fast in water)
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 phytophthora blight field guide
- Identify it
- Scout for it
- Control it
15 field-guide sections in the app
The full guide to phytophthora blight — 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 phytophthora blight?
The first thing you see: a plant that wilts and does not stand back up — even after you water it, even in the cool of the morning. Healthy plants droop in the midday heat and recover by evening; a blighted plant stays collapsed and dies within a few days.
When should I take action against phytophthora blight?
First wilting or stem lesions after heavy rain or irrigation; act immediately on drainage and remove affected plants (spreads fast in water)
How do I control phytophthora blight?
Prevent it first — this is your strongest defence (drainage + cultural care). Plant on raised beds or ridges so water drains away and never sits around the stem. Do not over-water and never flood-irrigate onto soaked ground. Rotate peppers, chillies, tomatoes, eggplants and cucurbits away from any bed that has had this blight — go 3–4 seasons into non-host crops (like cereals) before coming back. Start with clean, healthy transplants from disease-free ground.
Which crops does phytophthora blight affect?
Among the crops covered here: Eggplant, Sweet pepper, 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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