Downy mildew on cabbage
A fungal disease (Hyaloperonospora brassicae) that is most damaging in the seedbed and in early spring. It produces a white growth on the leaf underside with matching yellow patches on the upper surface.
Symptom photos
Symptoms
- A delicate, greyish-white growth on the leaf underside
- Yellow, angular patches on the upper leaf surface
- Patches browning and drying out over time
- Growth checked and seedlings dying in the seedbed
- Dark discoloration under the skin of cabbage heads
What it does to the crop
- Seedlings lost and gaps in the transplants
- Growth held back and smaller heads
- Poorer keeping quality
- The way opened for bacterial rots
What encourages it
- Cool nights and morning dew, temperature 8-16°C
- Humidity above 90%
- Dense sowing in the seedbed and poor ventilation
- Water staying on the leaves for long periods
Prevention
- Sow more thinly and ventilate the seedbed regularly
- Water in the morning so the leaves can dry
- Remove and destroy infected seedlings
- Rotate crops and clear away crop debris
- Grow less susceptible varieties
⚠️ Before you reach for a spray
This atlas is informational and still growing — different diseases can look almost identical. Confirm the diagnosis and read the product label before applying any plant protection product. If you are unsure, ask your local extension or advisory service.
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