Home Vegetable Gardening Potato Blight: Identification, Treatment, and Prevention

Potato Blight: Identification, Treatment, and Prevention

by Gregory
4 minutes read

Potato Blight: A Serious Fungal Disease

What is Potato Blight?

Potato blight, also known as late blight, is a devastating fungal disease that affects potatoes and tomatoes. It is caused by a fungus-like organism called Phytophthora infestans. Potato blight can cause significant crop losses, as it can spread rapidly and infect both the leaves and tubers of the plant.

Symptoms of Potato Blight

The first signs of potato blight are dark blotches on the leaves, starting at the tips and edges. These blotches will then spread, causing the leaves to shrivel and collapse. Blotches may also appear on the stems, which can turn black and rot. White spores may also be visible around the dark blotches and on the undersides of the leaves.

How Potato Blight Spreads

Potato blight spores are spread by the wind and can travel up to 30 miles. They can also be carried on infected plant material or in the soil. Blight is most likely to occur during warm, wet, or humid weather, as these conditions are ideal for the spores to germinate and spread.

Treating Potato Blight

There are both chemical and organic treatments available for potato blight. Chemical treatments, such as copper-based fungicides, were once commonly used to prevent blight, but have gradually been withdrawn from sale. Currently, there are no chemical treatments that can completely prevent potato blight.

Organic treatments involve removing infected plant material as soon as possible. This means cutting down the foliage and stems to ground level and leaving the tubers undisturbed for three weeks. This will help to kill off any lingering spores and prevent them from infecting the crop when it is lifted.

Preventing Potato Blight

There are several steps you can take to help prevent potato blight:

  • Grow early potatoes: Early potatoes are less likely to be affected by blight, as they can be harvested before the disease strikes.
  • Grow blight-resistant varieties: There are several varieties of potatoes that are resistant to blight. These varieties are less likely to develop the disease, even in wet conditions.
  • Practice good hygiene: Be sure to buy certified disease-free seed potatoes from a reputable supplier. Space plants further apart to increase air flow and help the foliage dry more quickly after rain. Water in the morning to avoid splashing the foliage, and earth up potatoes to help prevent the tubers from being infected.
  • Remove infected material: Remove any infected plant material from your garden or allotment and dispose of it properly. Do not compost infected material, as this may encourage the problem to persist the following year.
  • Practice crop rotation: Growing potatoes in a fresh piece of ground each year can help to avoid any disease build up in the soil.

Additional Information

  • Potato blight was responsible for the Irish potato famine in the 19th century, devastating crops and causing widespread hunger and death.
  • Potato blight is becoming increasingly common in the UK due to warmer winters and wetter summers.
  • There are several strains of potato blight circulating at any one time, and they are liable to merge and mutate.
  • Most infections in gardens and allotments are blown in from nearby plots, although it can also arise from infected material that has been left in the ground.
  • Tubers from blighted plants do not store well and should be used up as soon as possible. Discard any potatoes that show any signs of blight.

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