Downy mildew (Peronospora spinaciae / Peronospora farinosa)
This fungus is distributed worldwide. It causes leaf spotting that spoils the quality and appearance. Leaf spots begin as indefinite yellowish areas on the upper leaf surface. A mat of grey to violet mould develops on the corresponding lower surface. With time under cool, wet conditions, the spots enlarge until the whole leaf turns black and dies. The fungus increases profusely in high humidity. The spores can over-season in mild climates in living spinach, in seeds and in the soil.
- Use resistant varieties (e.g. "Early Hybrid 7").
- Use certified disease-free seeds. If using own seeds, treat seeds with 50 degC for 25 minutes.
- Practise at least a 3-year rotation and plant in well-drained soil.