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How to deal with scab potatoes


Scabbed potatoes lose about 30% of starch, their taste is made worse, and they are stored much less time. Since the diseased potato is in the ground, it is impossible to immediately notice and cure the disease when the potato grows. Because of this, it is very important to carry out activities for the prevention of the disease.

What is scab on potatoes

Scab - a disease caused by a fungus, usually more often affects the tubers, sometimes the roots and part of the stem, which is underground.

As manifested on potatoes

Scab on potatoes are divided into 4 forms: ordinary, silver, powdery and rhizoctoniosis (black scab).


For her, a favorable environment is alkaline or calcareous soil, which has a lack of moisture, while the air temperature is 25-30 gralus.
Common scab

The spores of the fungus penetrate the tuber through cracks in the peel. When storing the potatoes, they do not become infected, since the pathogens are in a state of rest under adverse conditions, but they do not die.

Common scab mainly falls on potatoes that have a scarlet or thin skin. If you plant potatoes deeply in the ground, water intensively with the growth of tubers, then the risk of getting sick decreases.

Symptoms: visible on the tuber crops hard ulcers of irregular shape, ulcers can cover the whole potato, or cracks are visible on the sore spots on the peel.


It often appears when potatoes are planted in sandy loam and loam, the optimum air temperature for the disease is 18–20 degrees, and the humidity is increased — 85–100%.

The fungus enters the tuber crops through the ground, then moves to the other potatoes. The difference of this form from others - diseased tubers do not rot in storage, but only lose moisture.

Symptoms: the skin is wrinkled, silver appears on the affected areas, especially brightly it is visible on the grades having a scarlet peel. Gradually brownish gray spots grow, sometimes they look depressed.

Sick potatoes barely germinate and the harvest is low.


She is most commonIt is a fungal pathogen that can move. The disease occurs on tuber crops, roots and the underground part of the stem.

When placed in storage, sick potatoes dry, but if the environment is excessive humidity, the potato rots. Often on diseased potatoes, late blight and dry rot are added to the scab.

Sources - land, diseased seed potatoes and manure (when feeding livestock to diseased potatoes, fungal spores do not lose activity even after passing through the digestion of a cow). The disease occurs in heavy land with excess water, at a temperature of 12-18 degrees.


Symptoms: whitish growths visible on the rootshaving a diverse shape, they are gradually made brown. On a sick tuber visible warts, a variety of spots. After some time, the diseased areas dry up, after the ulcers burst and appear, the gray-brown substance is visible in them - spores. More potatoes rot.

Rhizoctoniosis (black scab)

It can hit potatoes with high humidity and air temperature of 17 degrees, if there is often precipitation in the spring, and cold weather. Crop losses from black scab - 20-25%.

Symptoms: black spots on the tuber cropsresembling the ground, they can not be washed off the tubers and difficult to scrape, but they do not harm the tubers. Sick bushes during the day wither, grow low, they have twisted leaves. If it rains and it is warm, then a “white leg” is visible on the stem.


Where the disease comes from and how it develops

Scab - a disease arising from the fungus.

Causes of appearance:

  • Astonished land.
  • Sick tuber crops, on which the disease is not visible, but there is a fungus, since during the initial spread it is not visible.
  • Excess nitrogen in the soil stimulates the development of scab.
  • If you plant potatoes in one place from year to year, then diseases will accumulate in the ground.
  • High ground temperature.
  • Land having acidic properties.
  • Soil fertilizer before planting potatoes fresh manure.

How to fight


Maksim - This is a contact fungicide. Killing the fungus, Maxim preserves the beneficial microflora of the earth. 4 ml of Maxim are added in 0.05-0.1 l of water. Use, processing 10 kg of tubers.

Drug Maxim - an effective remedy for scab

To get rid of the disease, tuber crops are sprayed before planting:

  • 13 g Agata25K is added to 1 l of water, this composition is enough for 100 kg of potatoes;
  • 10 g of Fitosporin M is dissolved in 5 liters of water, using this rate per 20 kg of tubers;
  • 10 drops of Krezacin drip in 2 liters of water, use this composition per 40 kg potatoes.

Phytosporin sprayed bushes 3 times per season, in 1 package of drug add 3 l of water, then sprayed.

They take 25-50 grams of Kuprosat, add water to the ten-liter bucket, spray the bushes. The second time the bushes are treated 10 days later, but no later than 20 days before digging out the bushes.

Shrubs are also sprayed with drugs. Albit, Colfugo, Acrobat MC, Mancozeb, Profit Gold, Fenoram Super, Ordan.

This is done 2-4 times per vegetative season, as written in the instructions.


  • For planting take away absolutely healthy tubers. Handle the tubers before planting with special formulations.
  • Every year, change the place of planting potatoes, plant potatoes after beans, peas, beans. Do not use fresh manure as a fertilizer.
  • If you have an alkaline soil, then make it more acidic by adding a solution of 2 tbsp. spoons of ammonium sulfate in a ten-liter bucket of water and spilling the area. When flowering under one bush pour 0.5 liters of solution.
  • 14 days before digging potatoes mow the tops.
  • The room for storing potatoes should be dry and cool.

What potato varieties are considered highly resistant to the disease

  • Alyona - early variety. Tubers are oval, they have scarlet skin and snow-white flesh. Potatoes are resistant to scab, cancer, drought. But not resistant to late blight, it will have to fight.
  • Snow White - medium early variety. Good and long stored. It has resistance to scab and late blight. Oval tubers have yellowish peel and snow-white flesh, tiny eyes.
  • Resource - mid-season. Resistant to drought and heat. Almost not subject to viral diseases, scab. Resistant to mechanical damage. Tubers are oval with beige-skinned.
  • Lasock (Lasunak) - medium late, launched in Belarus. He has excellent taste, high yield. Resistant to scab, it almost does not hit the Colorado potato beetle.
  • Pace - late. Large, rounded-flat in shape with a creamy shade of skin and creamy hue of flesh, it tastes great. Resistant to scab.

In order for the potatoes not to be affected by scab, it is worth picking up for planting special varieties that are resistant to this disease, and also not to neglect prevention.