Preventing plant diseases
Most plant diseases are far easier to prevent than to cure. They take hold when plants are stressed, crowded or wet, so a few good habits stop the vast majority before they start.
What to look for
Sign | What it looks like |
|---|---|
Spots | on leaves or stems |
Mildew | white, powdery coating |
Wilting | despite moist soil |
Rot | soft, mouldy growth |
The common diseases
Damping off. Seedlings collapse at the base in cold, wet, still conditions. See Damping off and seedling mould.
Powdery mildew. A white, dusty coating on leaves, common in late summer and on dry-rooted plants. Improve airflow and keep the roots watered.
Blight. Brown patches on tomato and potato leaves and fruit in warm, wet spells. Space plants well and remove affected growth fast.
Rust. Orange or brown spots on leaf undersides. Remove affected leaves and avoid wetting the foliage.
Grey mould and rots. Fuzzy grey growth on soft, damaged or overcrowded plants. Tidy away dead material and improve airflow.
Why prevention beats cure
Disease loves damp, still, crowded conditions. Give plants room to breathe by spacing them to the distance on the packet, water at the base rather than over the leaves, and do it in the morning so foliage dries. Keep tools and pots clean.
Healthy soil grows resilient plants that resist infection.
If disease strikes
Act quickly. Remove and bin affected leaves or whole plants — not on the compost heap, where many diseases survive. Improve airflow, stop overhead watering, and give survivors space. Catching it early often saves the rest of the crop.
Building resilient plants
Strong plants rarely get sick. Feed the soil, space plants properly, rotate where you grow each crop family each year, and choose disease-resistant varieties where you can.
Frequently asked questions
Can I cure a diseased plant? Sometimes you can stop it spreading by removing affected parts, but prevention is far more reliable.
Can I compost diseased plants? Best not to. Many diseases survive composting.
How do I stop mildew? Improve airflow, keep roots watered, and avoid wetting the leaves.
Do resistant varieties help? Yes. They are bred to shrug off common diseases and are well worth choosing.
The full version of this guide is on seedschoice.com.
For a healthy garden
- Green manures for better soil
- Organic green manures
- Bee-friendly flowers
- Vegetables you can sow this month
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Updated on: 05/10/2026
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