Alternariosis of tomatoes: causes and treatment

Tomato Alternariosis is a disease caused by the fungus Alternatio solani Sorauer. Especially often the owners of greenhouses and residents of regions where hot weather gives way to rains are faced with a pathogenic microorganism. How to identify and prevent a dangerous disease?

Description

Alternariosis is one of the main diseases of tomatoes, which is also called dry or brown spot. It was first discovered at the beginning of the 20th century in the Kursk region. To date, the fungus infects tomatoes in the southern and central parts of Russia, as well as countries located in the southwest - Ukraine, Moldova.The average damage to the crop is 50%, and under the worst conditions, all 100%.

The progression of the disease is indicated by small brown spots that appeared first on the lower and then on the upper part of the plant.

The spots on the leaves are round, and on the stem they are elongated. Under the influence of dampness, the ulcers are covered with a barely noticeable black coating and slowly grow, merging into one large area.

The fungus affects not only large parts of the plant, but also flower stalks, sepals, a significant part of which is gradually covered with small round black spots. Due to extensive tissue necrosis, dry leaves fall off, and the damaged part of the stem often breaks, as a result of which the plant dies.

Tomato affected by Alternariosis is covered with depressed spots with a black coating.Most often, ulcers on fruits are located around the stalk or in places where the skin is damaged. The fungus also infects the core, which causes the tomato seeds to turn black and lose their germination. Affected fruits ripen prematurely or fall off.

Causes of occurrence

Just like all fungi, the Alternatio solani Sorauer mushroom actively develops in conditions of high humidity. Such conditions are created when summer days with a temperature of +24-+30 ⁰С are replaced by night rains. In greenhouses, the main catalysts for the development of pathogenic microflora are excessive watering and poor ventilation. Under such conditions, the incubation period for the development of the disease is 3-4 days. The yield of plants affected by Alternaria is reduced by 20-50%.

Alternariosis also develops on plants with mechanical damage. Conidia and mycelium that have entered the soil from the affected plant provoke diseases of tomatoes and other nightshade crops.

Especially often the fungus develops in film greenhouses and greenhouses on tomatoes with early ripening at high humidity.

How to prevent and cure?

As you know, the treatment of fungal diseases is a very difficult process. Therefore, in order to save yourself from a headache about the harvest, it is better to try to prevent the development of pathogenic microflora. To reduce the likelihood of infecting tomatoes with Alternaria, perform the following actions:

• After the end of fruiting, the bed is completely removed from plant residues, and the soil is carefully plowed.
• In greenhouses where tomatoes grow in the same place for several years, the soil is treated with a solution of potassium permanganate, copper sulphate or other disinfectant before sowing.

• Water plants under the root.
• Tie up medium and tall varieties, and remove leaves at the bottom of the plant.
• Alternate planting tomatoes with other plants. In the same place, the culture is planted 3 years after the previous time.

• Mixtures containing a large amount of potassium are used as fertilizers.
• Choose varieties with high immunity for planting. Sanka, Lyana, Golden Bullet, Luch are endowed with good immunity to Alternariosis. Among the tomatoes of hybrid origin, the seeds of Alex, Nadezhda, Aurora are planted.
• Use disinfected he althy seeds for sowing.
• With an interval of 2 weeks, tomato bushes are treated with fungicides. The number of sprays should not exceed 3-4.

Please note that you cannot choose a place for planting where eggplant, potatoes and other nightshade crops grew last season, as they are susceptible to the same diseases, including Alternaria.

Treatment of tomatoes begins immediately after the first signs of the disease are detected with contact fungicides. These drugs include Antracol 70 WG, Ridomil Gold MC, Ditan M-45, Quadris. When choosing a treatment, one must take into account the fact that not all preparations that include copper are suitable for the treatment of dry spotting.

Before purchasing a fungicide, you need to carefully read the instructions.

In addition to pesticides, biological preparations Fitosporin, Trichodermin are used for treatment. In case of untimely processing or its absence, the affected tomatoes die, and the fungus enters the soil and spreads to neighboring plants.

If you take preventive measures and treat diseased plants in a timely manner, the crop can be saved. The main rule of he althy plants in a greenhouse is the correct mode of watering and ventilation. Only those gardeners who comply with agro-technological requirements will be able to avoid crop loss.

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