Fungal disease
Potato Late Blight
A fast-spreading disease that can destroy potato foliage within days in warm, wet weather and rot the tubers.
Symptoms
- Dark, water-soaked patches spreading quickly across leaves
- White, fuzzy growth under the leaves in humid weather
- Brown lesions on stems, and reddish-brown rot in tubers
What causes it
Spores spread on wind and rain during warm, humid spells, and survive in infected tubers.
What you can do
- Remove and bag infected foliage; do not compost it.
- If the foliage is badly hit, cut it down to protect the tubers and wait two to three weeks before lifting.
- Grow resistant varieties.
- Do not keep or replant tubers from infected plants.
Not sure it's late blight?
Photograph one affected leaf and Plantulus will suggest the most likely problem, with a confidence score. It's free and needs no sign-up.
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General guidance only, not a diagnosis. Check product labels and local rules before using any treatment, and ask a horticultural specialist if a valuable plant is struggling. See the disclaimer.