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What is Potato Blight?

Rajib Singha Jun 30, 2019
This destructive potato disease is a common occurrence in agriculture. If one foresees the problem, it can be taken care of swiftly using efficient solutions, but one has to act soon, to save healthy potatoes in the blight's vicinity. Let's take an in-depth look at what potato blight is all about.
Every kind of plant remains susceptible to diseases, where the potato plant is no exception. Potato blight is one of the many potato diseases that is known to create havoc in the production of this tuber.
This disease occurs in two forms; early blight and late blight. The first one is caused by the organism Alternaria solani, and the other, by Phytophthora infestans (also known as water mold).
Among the two, late blight is reputed as a notorious potato plant disease. It is infamous for having caused large-scale deaths in the 1840s; the incident was known as the Irish potato famine.
Apart from this, it was also associated with other famines―the European, Highland, and Irish potato famines, respectively, during the same decade. These diseases not only jeopardize potato production, but they also affect tomatoes and other members that belong to the Solanaceae family.

Potato Blight Symptoms

Early Blight

  • Development of circular dark lesions (usually ½ an inch in diameter).
  • The lower and older leaves are the starting point of the disease.
  • Affected leaves wither, die, and then fall off.
  • Other symptoms include, the development of cankers on the stems, rotting fruits, and damping-off.

Late Blight

  • The leaves, stems, and tubers, are mostly affected by this disease.
  • The leaves develop lesions at the tips or margins. These make them look as if they were soaked in water.
  • With time, these lesions take on a black appearance with a purplish hue. A yellow halo may develop in some cases.
  • Lesions grow on the stems in circular manner, and are known to destroy foliage that grows above the stem.
  • A foul odor often indicates that the infestation is a severe one.


As soon as you notice the leaves getting affected, get rid of them. The best thing to do, is to burn the blight-affected leaves. Ensure that the plants are destroyed from the roots; this is to prevent the spores from invading the tuber.
After the affected leaves are destroyed, treat the plants with a fungicide. Inquire with you local garden center for the right kind that can effectively halt the spread of the blight. Usually, the fungicide needs to be diluted with water and then sprayed on the plants with a spray bottle; check the product's instructions to be sure.
If you notice that the infection is far too serious, then you may have to cut off the haulm, and burn it. The earth provides the tuber, protection, so don't worry about this step. Treating potato blight can get a bit tedious, where prevention, as they say, is the best cure.
Experts recommend the use of only seeds that have been certified to have been produced in places which are not prone to any plant diseases, caused by fungi and other pests. Wait for a span of 3 years before starting another potato plantation in the same spot.
While harvesting, it is a good practice to keep the soil free from any previously-diseased plant parts. This will ensure the soil is in a good state for the next plantation.