Alternaria tomato blight

Gardeners who decide to grow tomatoes on their plot often face the following phenomenon: spots, large and small, begin to appear on the foliage of tomato bushes. At first, their appearance may go unnoticed, or not worry the owner of the site until the spot spreads to the stems and fruits of the plants. Gradually, a black bloom appears on the spots, and the affected parts of the tomato bush die off, the plant dies. There is a risk of mistaking this ailment for late blight - a fungal disease characterized by the appearance of gray or brown-purple spots on plants. However, unlike late blight spots, the lesions described above
maintain clear contours and stay dry regardless of weather conditions. In addition, the appearance of these spots occurs at an earlier period of plant life than in the case of late blight disease. According to these signs, it can be established that the tomato beds were visited by another equally dangerous ailment - tomato alternaria. This article will discuss how to diagnose this disease in time, how to treat it, and what measures should be taken to prevent infection.

Alternaria blight of tomatoes. Briefly about the disease

alternariosis of tomatoes

Tomato Alternaria disease is known under such names as dry or brown spot, macrosporium, and refers to fungal infections. Alternaria solani Sorauer, a fungus that penetrates into plant tissues, is considered the causative agent of Alternaria.

Its conidiospores are dark gray and club-shaped. Forming chains, spores spread by asexual sporulation, giving infected tissues a dark gray or black color.

Tomato Alternaria affects all vegetative parts of tomato bushes. At an early stage, the disease can be diagnosed by dry, varied yellow spots with clear contours. As a rule, they are located along the edge of the sheet plate, occupying the tissue between the veins. But later they begin to increase in size and unite with each other.

The stems of tomato bushes are covered with brownish-gray spots of an elongated shape, slightly depressed into plant tissues. They gradually darken, acquiring a black color. In a similar way, the depressed spots covering the fruits are transformed: at first they are dark brown, over time they turn black, retaining their rounded shape.

The first symptoms of Alternaria appear even in the process of growing seedlings in a greenhouse. The first spots appear on the foliage located at the bottom of the plants. If you do not take action in a timely manner, the disease progresses and captures other parts of the bushes of tomato seedlings.

Getting on already formed fruits, spores of the fungus continue to multiply during storage of the crop, which can lead to its loss. Most often, Alternaria affects tomatoes in tomato greenhouses. The risk of infection is also present in the case of growing outdoors or in a film greenhouse.

At the same time, alternaria spreads in the phase of formation of fruit ovaries.

Factors due to which tomato disease occurs

alternariosis of tomatoes

The likelihood of infection with Alternaria is equally high at all stages of development of tomato bushes. The disease spreads with equal frequency to greenhouse seedlings, to plants planted in open ground, to flowering bushes, to tomatoes in the fruiting phase.

Temperature factor is of no small importance for the development of infection. The optimal conditions for the activation of fungal spores are warm, humid weather, when the thermometer does not drop below +25 degrees, and rainy days are replaced by dry ones.

Spores are carried by the wind and also spread through rainwater and irrigation. The peak of activity of pathogenic conidia occurs on those days when abundant dew is formed.
or there are intermittent rains. In these cases, moisture enters the plants without penetrating into the soil, which remains practically dry.

In greenhouse conditions, the spread of Alternaria is facilitated by irregular ventilation in
combined with high humidity.

Alternaria tomato blight - treatment

Having found the first signs of damage to tomato bushes by Alternaria, an urgent need to treat plants with one of the effective drugs. These include:

1. "Quadris, SC". It is a systemic pesticide and fungicide. The active substances penetrate the plant tissues through the pores on the leaf surface, inhibiting the development and spread of fungal spores, slowing down the process of their germination. This tool is suitable for both medicinal purposes and for preventive treatment of tomato bushes. The effect of its use is much higher in the early stages of the disease and begins to decrease with extensive damage to the tomato bush. The procedure for treating plants with the drug "Quadris, SK" is carried out by irrigation, and you should always use only fresh, just diluted solution. Its preparation must be carried out strictly according to the instructions. On average, 5 ml of the drug is enough for 10 liters of water. The volume of the mixture should be sufficient to moisturize the plant tissues, but the liquid should not drain to the ground.
2. Another pesticide and fungicide - "Acrobat MC", has a systemic contact mechanism of action. Release form - water-soluble granules. The substances included in its composition have a suppressive effect on the spores of the fungus, preventing their penetration and germination in plant tissues. It is recommended to start treatment at the first symptoms of Alternaria disease and repeat throughout the growing season. The interval between
   procedures range from 10 days to 2 weeks. A month before the planned harvest, measures for processing tomato beds should be discontinued. The preparation of the solution should also be carried out strictly according to the instructions. For 5 liters of water, as a rule, 20 g of the drug is consumed.
3. Another systemic drug - "Ordan", is available in powder form. Includes active ingredients such as copper oxychloride and cymoxanil. The first component helps to suppress the spread of fungal spores and is characterized by a long period of action. The second element penetrates into plant tissues and 60 minutes after treatment begins to inhibit disease-causing formations. "Ordan" is suitable as a medicinal
   measures, and for preventive treatment of plants. Most effective at an early stage of the disease. You can spray seedlings with them after 5 leaves appear. The interval between treatments should be about 14 days. You can harvest the crop 7 days after the last procedure. For spraying 1 are enough from 5 to 8 liters of solution.
4. "Sectin Phenomenon" - combined type fungicide and pesticide, produced in the form of water-soluble granules. It has an inhibitory effect on the development of fungal spores, prevents their germination in plant tissues. Suitable for both prevention and treatment of Alternaria at all stages of the disease. Differs in a long period of validity. Active substances infect pathogens throughout the crescent. In case of extensive lesions and rapid spread of spores, it is recommended to carry out treatment more often - weekly.
5. Another combined preparation of the fungicidal and pesticidal type is "Ridomil Gold Mts"... Protects plants from damage by spores of pathogenic fungi. Suitable for prophylaxis, destroys the causative agents of Alternaria. The advantage of the drug is its ability to protect not only the treated parts of the plant, but also new shoots that have appeared after spraying. Protects all parts of the plant, both internally and externally. Another plus of this drug is that it is poorly washed off by rains, it is effective even under adverse weather conditions. Release form - water-soluble granules. Has a wide spectrum of action - destroys the causative agents of Alternaria, late blight and peronosporosis.
6. Effective protection against Alternaria to plants is provided by a contact fungicide and a pesticide called "Poliram DF"... Preventive spraying with its solution stops the process of germination of fungal spores and their penetration into plant tissues of pathogenic microorganisms. At the first symptoms of Alternaria infection, diseased plants should be treated to prevent the spread of infection to neighboring bushes. During the entire growing season, it is recommended to use this preparation three times at intervals of a week or a little more. As soon as the first ovaries appear, it is necessary to stop spraying. For processing 1 hundred parts of a plot, 6 liters of solution are enough. "Polyram DF" has analogues like "Metiram" or "Mancoceba".

Preventive spraying

OLYMPUS DIGITAL CAMERA

The development of the disease and measures for its cure largely depend on the conditions in which the affected tomato bushes are located. Whether they grow in a greenhouse or outdoors.

A feature of greenhouse conditions is the creation of an ideal environment for the spread of fungal spores in cases where the ventilation regime is not observed. Stagnation of air and moisture invariably leads to increased sporulation. Therefore, the main measure to combat Alternaria in a greenhouse should be the Prevention of this disease.

Along with adjusting the ventilation mode, systematic spraying of greenhouse tomato plantings throughout the growing season is recommended. After the appearance of the ovaries, the procedure should be stopped.

For the treatment of tomato bushes growing in the open field, the already mentioned fungicides in the following dosage are best suited:

• Sectin Phenomenon - from 1 to 1.25 kg per hectare of land;
• "Acrobat MC" - 2 kg per hectare;
• Poliram DF and Ordan - from 2.5 to 3 kg per hectare;
• Ridomil Gold MC - 2.5 kg per hectare.

Preventive spraying should be carried out at the time of planting tomatoes in the beds. Or when the first symptoms of a fungal infection appear.

An effective way to reduce the risk of developing Alternaria is to cultivate the soil in the area with tomatoes. This can be done in two ways:

1. In the fall, you should thoroughly dig up the ground in the beds. That is, to carry out the so-called fall plowing of the area. The purpose of this procedure is to create unfavorable conditions for a pathogenic fungus. It is achieved by overturning soil layers. As a result, the process of decomposition of organic soil components starts. Mushroom being
   a source of alternaria, does not tolerate rotting. This is extremely important given that his disputes can
   successfully overwinter in plant debris and upper soil layers.
2. Another way to treat the soil is to disinfect it. You can carry it out using
   solution of Bordeaux mixture (3%), or a solution of contact-systemic fungicide "Oxyhom" (2%).
   The systemic-local fungicide "HOM" is also suitable. With a small degree of development of Alternaria, biologics can be dispensed with: "Trichomedrin", "Fitosporin", "Glyocladin".

Another way out for gardeners who want to reduce the risk of contamination of plantings with Alternaria is to plant varieties of tomatoes that are resistant to this disease. Doesn't exist at the moment
varieties that are 100% immune to this fungal infection. But there are a number of varieties
which are less susceptible to infection.

Among them - "The Little Prince", "Orange Giant", "Paradise Delight", "De Barao", "Liang", "Heart of America", "Salted Miracle".

Alternaria tomato blight, photos, preventive measures

Prevention of tomato disease with Alternaria includes several measures that are better
apply in a comprehensive manner in order to increase their effectiveness:

• Usage biologics will help to strengthen the immunity of plants, accelerate their growth, and have a positive effect on soil fertility. The biological protection provided by means such as Trichodermin is based on the spread of fungal spores hostile to the source of Alternaria. In the process of reproduction, its spores and mycelium work to produce antibiotics and nutrients that eradicate pathogenic fungal spores and other harmful formations and organisms. Treatment with biological products involves the introduction of a solution based on them during the planting of tomato bushes. About 4 ml of the product must be added to each planting hole, and also sprayed with a solution. When preparing it, you must strictly follow the instructions on the package.
• Burning plant residues Is an extremely important preventive measure. Since it is in the parts of plants infected with Alternaria that fungal spores remain. They can successfully overwinter in them, and become more active in spring. Therefore, the greens of tomato bushes remaining on the site and the fruits affected by the infection should not only be removed from the beds, but also burned. Do not forget about the already mentioned autumn plowing of the soil.
• Following the rules of crop rotation also contributes to a significant reduction in the likelihood of infection of tomato bushes with a fungal infection. It is worth paying close attention to the issue of choosing the predecessors of a particular culture. Tomatoes should not be planted in the beds where potatoes, eggplants, peppers, cabbage and tomatoes themselves were previously grown. The interval between planting these crops on one and the same place should be at least 3 years.
  You can plant tomatoes where spicy herbs, perennials, onions, cucumbers, any legumes grew in the previous season.
• Use of potash fertilizers, or complexes with a high content of this important macronutrient - another important point in the fight against tomato Alternaria. A complete nutritious diet generally improves plant health, and potassium is especially effective in increasing the resistance of tomato bushes to the effects of a dangerous fungus.

As in the case of other diseases, tomato Alternaria is much easier to cure at an early stage in the development of the disease, before the lesion has taken on a large-scale character. Better yet, prevent the formation of an environment conducive to the development of infection.

To do this, it is enough to follow a number of agrotechnical recommendations aimed at preventing this dangerous infection of fungal origin. If the spores of the fungus nevertheless penetrated into the tissues of the plant and began their destructive activity, there is a fairly large number of remedies. Whether it is folk methods or chemical preparations.