Potato scab is a fungal disease affecting tubers. Pathogens can be in the soil for a long time, and enter the vegetable through pores or small wounds. I immediately want to say that it is possible to eat an infected root crop, but the damaged part is cut off and thrown away. The danger of the appearance of scab is that the commodity and taste of the vegetable are reduced, the level of vitamins, minerals and amino acids is falling. 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 ° - 29 ° .
- Soil moisture - in the range of 50-70%.
- When making lime and wood ash.
- When fertilizing soil with manure. The danger is that when fighting scab, spoiled tubers are often used to feed livestock. Given that microorganisms are very stable, they pass through the digestive tract of the animal and exit along with its excrement. Fertilizing the soil with such manure can cause additional infection.
- With an excess of nitrogen-containing fertilizers and calcium.
- With a lack of soil boron and manganese.
Preventive measures to prevent the appearance of scab
It is best to immediately create and try to maintain conditions under which the causative agents of the disease 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 scab of potatoes. There are general tips for gardeners that can minimize the risk of developing the disease:
- Inspect planting material carefully . Choose large tubers weighing 75-100 g, pre-treated with a solution of boric acid (10 g per 9 liters of water).
- Deep root crops also reduce 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 by periodically sowing legumes after it, which enrich the soil with nitrogen and disinfect it. You can return the tuber culture to its former place after 4-5 years.
- Check soil acidity (pH should not exceed 6.0). Otherwise, crops can attack potato scab. Treatment chemical means does not produce results, but it is not difficult to reduce the risk of infection. You can adjust the pH by applying mineral fertilizers (superphosphate) under the tubers. Clearly follow the watering schedule. The application of lime is relevant only when the pH of the soil is below 4.9. It is useful to mulch potatoes with fallen pine needles, add sulfur (2.1 - 3.2 kg per one hundred square meters) or gypsum (15-20 kg per one hundred square meters).
These are just general guidelines. It is important for gardeners to know that there is a different scab on potatoes. The methods of struggle and development conditions may differ slightly, but in general the rules for eliminating the problem are the same.
Common scab
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, which gradually grow and eventually become covered with cork-like plaque.
Potato scab does not occur on all varieties. The most strong immunity to the disease are Berlichingen and Priekulsky, as well as Cameras.
Along with the general rules for planting and caring for the crop, there are several additions. Before how to get rid of scab of potatoes, 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 crops begins immediately after deepening into the soil and continues until the trunk of the plant grows to 1.5-2 cm in thickness.
Powdery scab
The causative agent is Spongospora subterranea. It develops in too wet soil. Moreover, the lumps of the pathogen can independently mix in the ground and reach the roots. Such a scab on potatoes manifests itself in the form of light gray warts .
The skin of the tuber cracks at the site of infection, the disease spreads further. It is believed that such varieties as "lorch", "jubilee", "cardinal" and "majestic" are practically not affected by the disease.
This potato disease is scab powdery - affects the roots and trunk. Tubers are susceptible to additional infection with late blight and the appearance of dry rot. Planting material before sowing is kept in a solution of 40% formalin (proportion: 1: 200) for 6-7 minutes, then covered with tarpaulin for a couple of hours.
Silver scab
First, brown spots or small patches appear on the tubers, resembling black soot. After peeling the potato peel, the stain acquires a gray tint.
The causative agent is the fungus Helminthosporium solani, which multiplies rapidly at a temperature of 19-21 ° C and a humidity of 90-95%.
The disease is dangerous in that the yield drops dramatically. Affected tubers continue to lose weight even when stored, and gray rot may appear at the site of the warts. Crops on loamy and sandy loamy soils are more susceptible to the disease. The tubers are pickled before planting. Processing is also carried out immediately after harvest before storage, using drugs such as Nitrafen, Botran, Fundazol, Celest or Titusim.
Rhizoctonia or Black Scab
The causative agent is Rhizoctonia solani. It develops in conditions of high humidity. As a rule, infection occurs if the spring is late and rainy. It manifests itself in the form of dark, deep spots or sclerotia, which are difficult to scrape off from the surface.
Black scab on potatoes it is dangerous because it can infect the tuber even at the germination stage. Such shoots either die, or appear on the surface with a defeat of the stem and twisted upper leaves. The causative agent feels best on loamy soils.
This is one of the most unpleasant variants of the disease, since resistant varieties do not exist. To prevent the black scab of potatoes from appearing, start treatment with the treatment of tubers with bacterial preparations such as Integral, Planriz or Bactofit, as well as with Fenoram, Vivatax or Maxim.
Planting depth: sandy loam soil - 7 cm, loamy soil - 8-11 cm, peaty soil - 12-13 cm. Maintain medium planting periods when the soil warms up to + 8 ° . Prevents the appearance of rhizoctonia in the application of mineral and organic fertilizers in doses slightly higher than recommended for this variety.