Downy mildew
Disease A damp-weather disease with yellow patches above and grey-purple fuzz below the leaf.
What to look for
Yellow or pale patches on the upper leaf surface, with grey or purple fuzzy growth underneath in humid weather. Leaves turn brown and die. Common on lettuce, spinach, onions, brassicas and basil.
When: Spring and autumn, or any cool, wet spell.
How to prevent it
- Space plants and avoid overhead watering.
- Water in the morning so leaves dry quickly.
- Rotate crops and clear debris at the end of the season.
- Choose resistant varieties, especially lettuce.
How to deal with it
- Remove and bin affected leaves, or the whole plant if badly hit.
- Improve airflow around crops.
- Sow successive crops in different spots, as the disease can build up.
Crops it affects
If you choose to use any treatment, use only products approved for UK home gardens, follow the label and avoid spraying open flowers. See all pests and diseases.