Tomato Blight

Tomato Blight

© Tony Austin

Type: Diseases

Blight (Phytophthora infestans)

A serious disease which affects first the top leaves, with brown blotches in late summer, in warm, wet weather. More often than not, the fungus then spreads down the stems killing the foliage.


  • Brown spots which begin on upper leaves
  • Brown patches on tubers, firm at first but quickly turning to a soft, wet rot

Prevention & control

  • Use certified disease-free seed potatoes
  • Grow resistant varieties
  • Grow earlier varieties which tend to have had more time to mature before blight hits
  • The disease spreads rapidly in warm, damp weather, so check regularly for symptoms from mid-summer onwards
  • It's always worth removing and burning the first few infected leaves, in case conditions turn drier, reducing the chances of further infection.
  • Tomatoes will generally develop dry brown rot too but potato tubers can often be spared if all foliage is cut down and burnt at when more than a few leaves have been infected. Mulching the soil may prevent the spores from getting to the tubers. Leave for a few weeks before harvesting to reduce chances of infecting tubers while lifting.
  • Infected tubers will rot in storage so check regularly
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