Why black spots may appear on tomato leaves in a greenhouse and how to get rid of them: we save the crop effectively

Vegetable growers who grow tomatoes in greenhouses often face various diseases of the nightshade family. Many diseases can be recognized by the main symptom - the appearance of spots on the leaves and fruits.

What to do if black spots appear on the leaves of tomatoes in the greenhouse, how to correctly identify the disease and what methods of dealing with it will help you cope with it - you will learn all this from our article.

Why do spots appear

The appearance of spots on the tops of tomatoes is a sign of the development of diseases: fungal, bacterial or viral. Some diseases can destroy the entire crop, so this symptom cannot be ignored. Infections are often transmitted from other garden crops such as potatoes and eggplants.

There are times when no abnormalities in the development of tomatoes or signs of disease are observed, and spots appear on the leaves. The problem may lie in the lack or excess of mineral fertilizers.

Important! Stains can appear due to improper care or if the place for the garden is not chosen correctly.

Light spots are not necessarily a sign of a disease, they can be the result of a plant being burned by the sun's rays. Also, they often appear when the roots of seedlings are damaged during transplantation.

Types of stains

Formations can be small, large, point-like, or completely cover the entire sheet. Such spots most often lead to thinning of the leaf plate and its drying.

With various rots, the spots are more moist and dense. Bacterial diseases are manifested by small formations that can acquire white, yellow, gray, brown and black color.

Diseases leading to spotting

To fix the problem, you must correctly determine the cause of its occurrence.

Such diseases lead to the appearance of spots:

1. Fungal: gray rot, phomosis, late blight, cladosporium, alternaria, goblet rust, septoria, root rot.
2. Bacterial: bacterial black spot, bacterial cancer, necrosis of the pith of the stem, wet rot, top rot.
3. Viral: chlorotic curl, mosaic, tomato streak.

Soil phytotoxicity

The formation of stains on seedlings is possible due to improper use of pesticides and fertilizers. The imbalance of substances negatively affects the development and productivity of the plant. Lack of calcium is one of the factors leading to the development of various diseases.

Determining the cause

Each disease has its own distinctive symptoms. It is important to learn how to correctly determine the source of the appearance of spotting on tomatoes so as not to harm the seedlings.

Bacterial diseases

Bacterial spotting is caused by Xanthamonas microorganisms, which have 4 phenotypes. Bacteria can be found in seeds and plant tops. These microorganisms do not live long in the soil. The disease progresses at a humidity above 70% and an air temperature of 25-30 ° C. If you don't take action right away, the plant will dry out.

The main signs of bacterial diseases:

• the appearance of olive dots of an oily consistency;
• formations acquire a dark shade with an external light rim;
• the size of the spots is 5-6 mm;
• both stems and fruits can be affected;
• the plant loses 50-100% of its leaves.

With black bacterial spot, plants look stunted, underdeveloped. Pith necrosis is identified by brown spots that begin to crack over time. With wet rot, the stems and fruits acquire a brown color and soften - the plant begins to rot from the inside.

Bacterial cancer is characterized by the appearance of small white spots on the fruits, wilting of leaves and the formation of brown growths on the petioles.

Top rot can be recognized by the formation of a dry brown spot on the top of unripe fruits, which increases in size over time. The green mass does not suffer from this disease.

Fungal diseases

The spots are formed due to the activity of fungi. The defeat of the plant begins with the stem; in the initial stages, the gardener may not immediately recognize the threat. The pathogen spreads rapidly and infects leaves and fruits. The disease is typical for greenhouses and hotbeds.

Factors provoking the development of the disease: high humidity, abundant watering, high air temperature, an excess of nitrogenous fertilizers.

Important! In case of fungal diseases, the plant may die 5-10 days after infection.

Diseases caused by fungi:

1. Gray rot- gray spots form on the plant, white fluffy bloom and rotting areas appear on the fruits.
2. White rot- tomatoes begin to crack, soften and become covered with white spots. The disease rapidly spreads to the leaves and stem: the leaf plate becomes thinner, loses its color, white dots and spots are formed.
3. Fomoz- small brown or black spots appear on the leaves, which gradually increase in size and darken. Concentric circles form on the stems, brown spots appear on the fruit near the stalk.
4. Late blight- spots appear in the lower part of the stem, then the disease affects the leaves and fruits. The green mass, flowers and ovary dry up and fall off.
5. Cladosporium- gray or olive spots with a fluffy bloom are formed on the lower part of the leaf, small yellow formations on the upper part. Leaves, flowers and ovary dry up and fall off.
6. Goblet rust - yellow dots appear on the leaves, which gradually increase and acquire a rusty color. The diseased plant is deformed and dries up.
7. Alternaria or macrosporiosis- rounded yellow-brown spots are formed on the leaves, gray-brown on the stems. The size of the spots is up to a centimeter. Fruits may be affected. The disease manifests itself immediately after planting seedlings in the ground.
8. Septoriasis- even gray or white spots with a dark border appear on the leaves. The disease first affects the lower leaves and then spreads throughout the plant. The green mass curls, dries up and falls off.
9. Root rot - the area of ​​the root collar becomes black, rusty spots appear on the trunk, the foliage is covered with a white bloom, after which the plant withers.

Viral diseases

Tomatoes most often affect the following diseases:

• tomato streak- light areas of necrosis appear throughout the plant, resembling strokes. Over time, the formations merge, the green mass dries up, and the fruits crack;
• mosaic- manifests itself in speckled leaves, some areas become white, others dark. Outgrowths form on the underside of the leaflet, tomato necrosis occurs;
• chlorotic curl- a type of mosaic caused by a virus carried by whiteflies. In addition to the appearance of spots of various shades, the leaf plate can curl, which is why the bush acquires curliness.

Ways to fight

Each disease requires its own approach and method of treatment.

Bacterial diseases

The development of bacterial diseases can be prevented by seed treatment. For prevention use:

• 3-5% sodium hydrochloride;
• 6-8% calcium hydrochloride;
• trisodium phosphate.

Important! The material is soaked in hydrochloride solutions for 10-30 minutes, in trisodium phosphate for 60 minutes.

Seedlings and adult bushes are treated with such preparations:

• Fitolavin;
• Fitosporin-M;
• "Acrobat";
• "Baktofit";
• "HOM";
• bordeaux liquid.

Fungal diseases

For fungal infections, fungicides are used, bordeaux liquid, copper sulfate and garlic infusion.

1. The following drugs are effective against gray rot: "Acrobat MC", "Profit Gold", "Abiga-Peak", "Previkur". As a preventive measure, the beds are treated with copper sulfate, garlic infusion and Bordeaux liquid.
2. A plant that has become infected with white rot is pulled out and burned. Drugs against this disease are not effective. The best protection is prevention: heating the seed in the oven or processing with a manganese solution. Before planting seedlings in the ground, disinfection is carried out with copper sulfate, urea or zinc sulfate.
3. Phomosis is not treated - tomatoes are pulled out and burned, and the soil should be disinfected. To reduce the likelihood of developing the disease, it is important to control the humidity of the air, to avoid the use of manure and nitrogenous fertilizers.
4. Late blight is treated with drugs: "Previkur", "Findazol", "Horus", "HOM", "Topaz" and the antibiotic "Trichopol". The treatment of seedlings with Bordeaux liquid, copper sulfate, garlic infusion and manganese solution also helps. At the end of the season, all plant residues are burned and the soil is disinfected.
5. With cladosporium the affected leaves are cut off, the plants are treated with the preparations "HOM" and "Effekton-O". The fungus can also be removed using Bordeaux liquid, copper sulfate and garlic infusion.
6. Goblet rust you can win with the help of such drugs: "Oxyhom", "Figon" and "Fundazol". Folk remedies are also effective: infusion of marigolds or horsetail, soda ash.
7. Alternaria are treated with fungicides: "Ditan-M45", "Antrakol-70", "Quadris", "Infinity", "Flint".
8. With septoria the affected tomatoes are destroyed, the greenhouse and the soil are disinfected. Prevention is spraying the beds with a 1% solution of Bordeaux liquid or 0.3% suspension of copper oxychloride.
9. Root rot are treated with the drug "Ridomil Gold", to prevent the disease, seeds, soil and seedlings are treated with the drugs "Pseudobacterin-2" and "Rossa".

Viral diseases

Diseases of tomatoes caused by viruses are virtually untreatable. We recommend choosing varieties that are resistant to diseases: Semko, Madison, Sors, ​​Zhenaros, Anyuta, Kunero.

At the initial stage of the mosaic, a solution of whey with the addition of "Pharmayod-3" will help to save the harvest. From chlorotic curliness, the bushes are treated with the preparations "Citkor" and "Fitover". With the further development of the disease, the plants are pulled out, disinfected with trisodium phosphate, and then burned.

Tips from experienced gardeners

Vegetable growers recommend not to neglect simple rules that will help protect seedlings from diseases and phytotoxicity of the soil:

1. Purchase seed material from a trusted manufacturer and at certified retail outlets.
2. Always process seeds before planting.
3. Do not neglect soil disinfection - disinfection is carried out before planting seedlings and after harvesting.
4. Observe the rules of crop rotation - tomatoes are planted on the previous bed only after 3-4 seasons.
5. If the site is located in an arid area, peat or sod land should be introduced into it before planting seedlings.
6. Do not thicken the planting - 70 cm should remain between the plants.
7. Cut out weeds in a timely manner.
8. Do not flood plants with water.
9. Mulch the tomato beds with straw or plastic.
10. Ventilate the greenhouse regularly.
11. Disinfect garden tools.
12. Monitor temperature and humidity indicators.
13. Control the amount of nitrogenous fertilizers.
14. Destroy aphids - a carrier of pathogens.
15. Burn all plant residues after harvest.

If the disease still manifests itself, it is important to start treatment immediately. Delay in this matter will lead to crop loss.

Conclusion

There are many reasons for the appearance of spots on tomatoes. The symptoms of bacterial diseases are similar, so the same drugs are used in the treatment. Fungal diseases are more diverse and there are many medicines for them, but pathogens react in the same way to Bordeaux liquid, copper sulphate and garlic infusion.

Treatment for viral diseases is useless - the plants are destroyed, and the beds are disinfected. Reviews of vegetable growers show that one should not neglect preventive measures, they are the key to obtaining a bountiful harvest.