Alternaria is a genus of mold fungi that affects many plants, which ultimately leads to the impossibility of eating their fruits, in addition, it is one of the causes of many human diseases, such as various allergies and bronchial asthma. This article is fully devoted to the development of alternaria in potatoes, it contains a photo with its symptoms, a general description of the disease and methods of its treatment.
Description
This disease is often infects tubers, stems and leaves of plants. Alternariosis is not a disease characteristic exclusively of potatoes, it can also affect other plants that belong to the Solanaceous family, for example, tomatoes. The damage caused by this disease, comparable to the damage from late blight, can reduce the overall yield by 20-30%.
Did you know? South America is considered to be the birthplace of potatoes, where you can still meet its wild representatives. However, for several tens of thousands of years, Indians of South America have grown potatoes as a cultivated plant.
Before the onset of flowering, usually in 15-20 days, on the leaves of the affected potato are formed large brown or dark brown spotswhich have a concentric structure. If the degree of damage is high enough, the spots begin to merge with each other, and the leaves begin to rapidly turn yellow and fall off. The stalks and stalks of affected plants also have spots on their own which are generally similar in structure, but more elongated. 
If the environment is favorable (temperature from + 26 ° C and sufficient humidity) for the development of the disease, then the first spots begin to appear on infected plants after 2-3 days from the moment of infection.
The tuber of the affected potato is covered with irregular spots, often depressed, which have a darker shade than the skin. Healthy tissue is very different in structure from the affected. Very large spots are covered with a network of wrinkles arranged in a circle shape and wearing a parallel direction.
If you cut an infected tuber, you can clearly see areas of necrotic tissue that rot in a manner similar to dry rot. They resemble in their structure a dense, dry, brown-black solid mass. 
Causes and pathogen
The cause of the disease is hit on only planted new potatoes conidia and mycelium, remaining on the remains of plants and tubers. As soon as the weather conditions contributing to the further development of the fungus occur, the disease begins its active development.
Did you know? At the moment there are about 44 described species belonging to the genus Alternaria, however, according to some assumptions, there are much more, up to several hundred.
Most common pathogens - A. solani, a. alternata, a. infectoria and others of this kind. The mycelium of all these species has approximately the same appearance: it is an interlacing of thin bleached fibers, has a rather branched structure, septate. 
The reasons contributing to the development of the disease include: weakening of plants by adverse soil or weather conditions, too dry and hot weather, lack or excess of moisture, soil poverty, insufficient amounts of potassium and excessive phosphorus, contamination of your seed by various diseases.
Tips for novice gardeners: learn how to grow potatoes under straw, in bags, before winter, according to Dutch technology; how to spud (including motoblock) and feed; what siderata better to plant a potato.
Resistant varieties
Alas, the breeders have so far failed to develop a variety that would not be afraid of such a potato disease as alternariosis. However, there is a list that includes varieties that are subject to this ailment. less than others:
- Adretta This potato, besides its opportunistic properties in relation to Alternaria, is also famous for the fact that it is the first variety with yellow flesh, which was intended for human consumption. Best suited for jacket cooking.
- Bronnitsky. In addition to the high resistance to the hero of this article, well against such diseases affecting potatoes, as a black leg and scab. This variety is best suited for frying french fries.
- Love. A fairly early variety that has white tubers, a characteristic feature of which is that they do not lose their whiteness during the cooking process. Despite its significant resistance to Alternaria, it is often affected by common scab.
Read also about the varieties of potatoes: "Kiwi", "Luck", "Gala", "Queen Anne", "Rosara", "Blue", "Irbitsky".
How to deal with Alternaria
If you notice that your plants are sick with Alternaria, it's time to try to save the potatoes, using some control measures. Such measures include two large groups of manipulations - they are processing with the help of various biological means and spraying with various chemical means.
Biological agents
This method of struggle involves the processing of tubers in advance before planting. Often, various spray guns are used, in which special preparations are added, after which the spraying takes place directly.
Most suitable spray products before the landing period, these are Baktofid, Integral and Agat-25. And if you intend to reduce the infection of tubers after the onset of the growing season, then you should use the drug "Planriz". 
Chemicals
The use of this group of substances, as a rule, is a significant threat to human health due to their toxicity. Therefore, when spraying these drugs, it is necessary to remember about personal protective equipment: a protective suit, gloves, goggles and a mask or respirator.
Processing this group of drugs involves spraying them during the growing season. For this purpose, 0.2-0.3% solutions of such preparations are best suited:
- "Profit",
- "Novozri",
- "Thanos",
- "Mancozeb",
- "Kuproksat",
- "Uten",
- "Penczeb".
It is also possible to use 0.4-0.5% solutions of Metaxax, Cupricol, Acrobat MC, HOM, Metamil, and Abigak-Pika.
Important! If you notice that your potatoes are infected with Alternaria in the early stages of its development, then you can use the drug to treat it. "Bravo" at the rate of 2.3-3 liters per 1 hectare of landing area.
It is also possible to sprinkle tubers in the period preceding their laying for winter preservation with the help of the “Maxim” preparation at the rate of 0.2 l per 1 ton. The initial treatment should be done immediately after the discovery of the first signs of the disease. Further frequency of spraying depends on the duration of the selected drug and the temperature conditions in which the potato is located. 
Disease prevention
There is a wide range of possible preventive methods this disease, the most important of which are listed below:
- Thorough cleaning of the future planting of potatoes from the remnants of diseased plants. To this end, deep winter plowing will serve the best, which very well helps plant residues to decompose properly, which prevents the accumulation of harmful spores and mycelium in the soil.
- It is necessary to comply with the rules of crop rotation, not planting a number of potatoes and members of other families of the Solanaceae, such as tomatoes, which are also susceptible to this disease.
- You should not grow potatoes for more than three years at the same place.
- Correct and timely application of fertilizing. The soil must be perfectly balanced for growing potatoes, contain sufficient, but not excessive, nitrogen and potassium.
- If year after year your tubers are affected by this disease, then try to grow varieties that are resistant to this disease. A list of such varieties can be found above.
- Remove the tubers only after they are fully ripe, trying not to cause them mechanical damage. So you will increase the likelihood that a part or a whole tuber will remain in the soil, which will later serve as a hotbed for this fungus.
Important! Remember that you can not sprinkle your potatoes too often. The greatest number of treatments - four per season.
We hope that this article will help you to cope with such an unpleasant disease, as alternaria disease of potatoes. Remember that the time spent prevention - much more effective than any, even the most expensive treatment, it is much better to help you save your potato harvest than the most modern drugs. Have a good harvest!
