How To Prevent And Treat Potato Blight

Any gardener will tell you, there’s nothing more annoying than potato blight. It thrives in humid weather and is caused by a fungus called Phytophthora infestans that spreads through the air. With the weather starting to slowly pick up, it’s important to learn how to prevent this pesky fungus.

How does one prevent and treat this fungus? Here, our garden expert, Paraic Horkan, shares all of his expert information and knowledge on the prevention and treatment of potato blight.

Causes of Potato Blight:

  • It’s caused by a fungus called Phytophthora Infestans
  • The fungus affects members of the potato family, including tomatoes, peppers and aubergines.
  • It spreads through the air, developing when the weather conditions are warm and humid.
  • Periods of warm, humid weather increases the risk of potato blight.
Potato Blight on leaf
Potato Blight on potato

Potato Blight can be spread through the air and in water. Wind carries spores of the disease from plant to plant. Water can wash the spores into the soil, where it can infect young tubers.

Potato Blight is a destructive disease. It can wipe out a full crop of potatoes overnight. In a sack or a crate, it will travel from potato to potato, infecting them all. The fungus is generally killed by cold weather, but there are some rare resistant strains that survive over the winter.

Symptoms of Potato Blight: 

  • Brown freckles or patches on the potato leaves
  • Yellowish border spreading from the brown patches
  • Dark patches on the tubers
  • Inside of the tubers are brown or rotting
  • The potatoes will turn soggy and excrete a foul-smell
Potato Blight on tuber

Preventing Potato Blight:

  • The best way to prevent potato blight is to plant a blight-resistant variety. Some of our favourites include Colleen, Golden Wonder and Kerr’s Pink.
  • Make sure potatoes are well earthed to prevent spores getting into the tubers.
  • Spray leaves and stems with a preventative treatment such as Bayer Garden Blight Control.
  • Check regularly for symptoms of infection (as outlined above).

How to use Bayer Garden Blight Control?

Bayer Garden Blight Control is effective against the early stages of Phytophthora Infestans. You simply spray your plants to protect them from the blight fungus spores. It is rain-fast within 1 hour, so should be applied immediately. For maximum protection from potato blight, crops should be sprayed four times a year, with 10 day intervals. This will protect the leaves, stalks and also the tubers from the risk of late blight infection after harvest. Each 100ml bottle of Bayer Garden Blight Control will treat up to 625sqm.

Treatment of Potato Blight: 

  • If only a small number of leaves are affected, you can remove and dispose of them.
  • Spray with Bayer Garden Blight Control, which can be used up to four times per growing season.
  • If the infection has spread,  cut the foliage and stems. 
  • Removing the foliage prevents the disease from getting into the tubers, as long as they are well covered with earth.
  • Leave the crop for at least two weeks to let the blight spores on the surface die and the potatoes to develop a thicker skin.
  • After harvest, check regularly for signs of blight and remove any suspect tubers from your store, immediately. 

If you’d like to learn more about growing potatoes, just read our blog here. Do you have questions about potato blight? If so, just contact your local store where one of our helpful and knowledgeable staff will be happy to help and answer any questions you may have.