Potato and tomato blight
Large brown to black patches on the leaves and stems of potatoes and tomatoes, with a white fringe underneath in damp weather. The foliage dies within days; tomatoes get hard brown patches and potatoes rot.
Phytophthora infestans spreads very quickly on the wind in warm, humid weather, usually from July.
What can you do?
- Remove affected leaves straight away; if potato foliage is badly hit, cut it down and take it away.
- After cutting the foliage, wait two weeks before lifting so the tuber skins harden and don’t get infected.
- Put diseased plants, fruit and tubers in the green waste bin or general waste, not on your compost heap.
- Grow tomatoes under cover or in a greenhouse and water at the base to keep the leaves dry.
Prevention
Choose resistant potato and tomato varieties, wait four years before growing them in the same spot again and remove volunteer potatoes. Don’t grow tomatoes next to potatoes.
When to watch out: July–September