Lesson 5
Fungal diseases — mildew, blight and rust
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Fungal disease is almost always a sign of stagnant air or wet leaves overnight. Containers help because we can move them — open beds we can only prune.
Prevention and rescue
- 1Water the soil, never the leaves; water in the morning so leaves are dry by night.
- 2Space plants for airflow — when in doubt, give them more room.
- 3Mulch to keep soil moisture even (mildew loves dry roots and damp air).
- 4Remove and bin (not compost!) any infected leaves at the first sign.
- 5A weekly milk-spray (1 part milk to 9 parts water) is a surprisingly effective preventative for mildew.
Three fungi every grower meets
- Powdery mildew — white dust on leaves of courgette, cucumber, basil. Cause: dry roots + humid air.
- Tomato/potato blight — brown patches with grey fuzz; spreads in warm wet July weather. Cause: spores on damp leaves.
- Rust — orange spots on undersides of leaves of mint, garlic, hollyhocks. Cause: water on foliage, crowded plants.
If blight strikes mid-season, cut every leaf off the affected plant. Yes — strip it. Many tomato plants will still finish the fruit they have.