Scab on potatoes is a fungal disease that affects tubers. Pathogens can stay in the soil for a long time, and enter the vegetable through pores or small wounds. I want to say right away that the infected root crop can be eaten, but the damaged part is cut off and thrown away. The danger of the appearance of scab lies in the fact that the commercial and palatability of the vegetable decreases, the level of vitamins, minerals and amino acids decreases. If the loss of nutrients is 35%-40%, then the yield is reduced by half (in some cases, losses reach 60%-65%).
Favorable conditions for the development of the disease
Like any ailment, scab occurs in certain cases. Among them are the following:
- soil pH 6, 1 - 7, 4, that is, the reaction is slightly alkaline.
- Air temperature 24°С - 29°С.
- Soil moisture is within 50-70%.
- When applying lime and wood ash.
- When fertilizing the soil with manure. The danger lies in the fact that in the fight against scab, spoiled tubers are often used to feed livestock. Given that microorganisms are highly resistant, they pass throughthe digestive tract of the animal and are excreted along with its excrement. Fertilizing the soil with this manure can cause additional infestation.
- With an excess of nitrogen-containing fertilizers and calcium.
- With a lack of boron and manganese in the soil.
Preventive measures to prevent scab
It is best to immediately create and try to maintain conditions under which pathogens will be uncomfortable. But if you still notice small convex warts on the tubers, then be sure to find out how to get rid of potato scab. There are general tips for gardeners that can minimize the risk of developing the disease:
- Carefully inspect the planting material. Choose large tubers weighing 75-100 g, pre-treated with a solution of boric acid (10 g per 9 liters of water).
- Deep seeding of root crops also reduces the risk of scab.
- After harvesting, it is necessary to collect all residues (spoiled tubers, roots, stems) and destroy them.
- The potato planting site must be changed, periodically sowing legumes after it, which enrich the soil with nitrogen and disinfect it. You can return the tuber culture to its original place in 4-5 years.
- Check soil acidity (pH should not exceed 6.0). Otherwise, potato scab may attack crops. Treatment with chemicals does not work, but it is not difficult to reduce the risk of infection. You can adjust the pH by applying mineral fertilizers (superphosphate) under the tubers. Follow the watering schedule carefully. Lime applicationrelevant only when the soil pH is below 4.9. It is useful to mulch potatoes with fallen pine needles, add sulfur (2.1 - 3.2 kg per hundred square meters) or gypsum (15-20 kg per hundred square meters).
These are just general guidelines. It is important for gardeners to know that there are different scabs on potatoes. The methods of struggle and development conditions may differ slightly, but in general, the rules for eliminating the problem are the same.
This type of disease is more common than others. The causative agent is Streptomyces scabies. It develops well in sandy and calcareous soils, in conditions of high humidity and large doses of organic matter. The onset of the disease is easily diagnosed by small ulcers that gradually grow and eventually become covered with a cork-like coating.
Common scab on potatoes does not occur on all varieties. Berlichingen and Priekulsky, as well as Kameraz, have the strongest immunity to the disease.
Along with the general rules for planting and caring for a crop, there are several additions. Before getting rid of potato scab, carry out preventive treatment of tubers - sprinkle them with Nitrafen or Polycarbacin. Germination of planting material in the light helps very effectively in the fight against the disease. Watering the crop begins immediately after deepening into the soil and continues until the stem of the plant increases to 1.5-2 cm in thickness.
The causative agent is Spongospora subterranea.Grows in too wet soil. Moreover, lumps of the pathogen can independently mix in the ground and reach the roots. Such scab on potatoes appears as light gray warts.
The skin of the tuber cracks at the site of infection, the disease spreads further. It is believed that varieties such as "lorch", "yubel", "cardinal" and "majestic" are practically not susceptible to the disease.
This potato disease - powdery scab - affects the roots and trunk. Tubers are susceptible to additional late blight infection and dry rot. Planting material before sowing is kept in a solution of 40% formalin (proportion - 1:200) for 6-7 minutes, then covered with a tarpaulin for a couple of hours.
First, brown spots or small areas resembling black soot appear on the tubers. After peeling off the skin of the potato, the stain becomes gray.
The causative agent is the fungus Helminthosporium solani, which multiplies rapidly at temperatures of 19-21°C and humidity of 90-95%.
The disease is dangerous because the yield drops dramatically. Affected tubers continue to lose mass even during storage, and gray rot may appear in place of warts. Crops on loamy and sandy soils are more susceptible to disease. Before planting, the tubers are dressed. Processing is also carried out immediately after harvesting before storage, usingdrugs such as Nitrafen, Botran, Fundazol, Celeste or Titusim.
Rhizoctoniosis, or Black scab
The causative agent is Rhizoctonia solani. Develops in conditions of high humidity. As a rule, infection occurs if the spring is late and rainy. Appears as dark, deep spots or sclerotia that are difficult to scrape off the surface.
Black scab on potatoes is dangerous because it can infect the tuber at the germination stage. Such seedlings either die or appear on the surface with stem damage and twisted upper leaves. The pathogen feels best on loamy soils.
This is one of the most troublesome variants of the disease, as there are no varieties resistant to it. To prevent the black scab of potatoes from appearing, start the treatment by treating the tubers with bacterial preparations such as Integral, Planriz or Bactofit, as well as Fenoram, Vivatax or Maxim.
Planting depth: sandy soils - 7 cm, loamy soils - 8-11 cm, peat - 12-13 cm. Maintain the average planting time when the soil warms up to + 8 ° С. Prevents the appearance of rhizoctoniosis by applying mineral and organic fertilizers in doses slightly higher than those recommended for this variety.