Plant guide:🍅 Tomato
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⚠ CriticalRapidly spreading water-soaked grey-green patches � one of the most destructive tomato diseases, capable of killing a plant within days.
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Fungal
Late Blight on Tomato Plants
Commonly affects: Solanum lycopersicum (Tomato)
Large, irregular, water-soaked grey-green patches spread rapidly across leaves, often with a white fuzzy mould visible on the underside in humid conditions. Stems can develop dark lesions, and fruit shows firm, brown, irregular blotches. The disease can destroy an entire plant within days.
Potential Causes
- 1Phytophthora infestans, an aggressive water mould that spreads via airborne spores over long distances
- 2Cool, wet weather with high humidity, which favours rapid spore germination and spread
- 3Infected transplants or nearby infected potato plants, a common alternate host
Solution Steps
- 1Remove and destroy affected plants immediately � do not compost them, since spores can survive and spread.
- 2Act fast: late blight can spread through a planting within days once conditions favour it.
- 3Apply a copper-based fungicide preventively to remaining healthy plants if late blight has been reported in your area.
- 4Avoid overhead watering and improve airflow between plants to reduce the humid conditions the disease needs.
Prevention Tip
Monitor local blight warnings during cool, wet weather, and act immediately at the first sign of grey-green watery patches � late blight can destroy a planting within a week if left unchecked.
