Late blight on tomatoes: signs and causes of appearance, methods of treatment

What is late blight?

Late blight or late blight is a common fungal disease that affects about fifty garden crops. Tomatoes suffer more than other vegetables. The fungus spreads by spores and is capable of quickly and en masse infecting tomato plantations. A couple of days are enough for all the bushes to be infected.

The fungus attacks the fruits and leaves of bushes, which leads to a significant reduction in yield. For the time being, the pathogen hides in the ground. It becomes active only in the second half of July, when summer nights become damper and cooler.

Tomato varieties that are not afraid of late blight

There are no varieties yet that show complete resistance to this harmful disease. But some, early ripening ones, manage to harvest before a mass outbreak of the disease. And there are so-called blight-resistant varieties, most often these are new-generation hybrids, which, with proper agricultural technology, rarely become infected with fungus, even if diseased bushes grow nearby. The list is as follows:

White filling
Blizzard
Kostroma
Siberian early ripening
Budenovka
Oak
Pink dwarf
Harvest
Dubrava
All types of De Barao
Cold resistant
Tarasenko hybrids
Solar
Cameo
Pepper-shaped
Etoile
Berry
Combitomat
Ballad
Masterpiece 1
Liana
Ephemera
Vladimir Vysotsky
Yablonka Russia
Sprint Timer, etc.

Hybrids and hybrid varieties

Lark F1
Chimgan F1
Cupero F1
Black bunch F1
Zhenaros F1
Honey drop F1

How does the disease manifest itself on tomatoes?

The presence of late blight on plants can be guessed by the characteristic symptoms. True, when signs of the disease appear, crop losses cannot be avoided.

Symptoms of late blight:

the fruits are covered with black or gray-brown spots;
later, the affected fruits rot and emit an unpleasant odor;
Dark spots first appear on the leaves, then they dry out and fall off;
brown spots appear on the stems;
during rain, the leaves of bushes affected by late blight become shiny and oily;
Tomato flowers become dark, dry out and fall off.

Why can't it be detected in time?

Late blight can completely destroy tomato tops and fruits

The main problem for beginning farmers is the inability to recognize late blight in its early stages. Usually, the realization that a disease is rampant in a tomato plot comes when most of the fruits are covered with dark spots. Unfortunately, at this stage it is almost impossible to save the bushes.

The incubation period of late blight is very short and under favorable conditions (temperature 20 - 25 degrees, relative humidity 90 - 95%), the disease can infect plants in 3 - 6 days.

For some reason, most gardeners are confident that the onset of the disease is the simultaneous appearance of brown or brown-black spots on leaf blades, stems and fruits. In fact, this is a huge misconception.

The first manifestation of late blight is a change in leaf color. Light green areas appear on them, differing from the main color by literally 2 to 3 tones.

And only after a few days they begin to turn yellow and dry out. After damage to part of the leaf apparatus, late blight spreads to the stem, forming dark areas on it, which gradually merge into a solid black spot. The development of late blight never begins with tomato fruits.

If you detect the disease at the initial stage, then stopping its development is not so difficult. Copper-containing preparations make it possible to defeat late blight at this stage in just one treatment. However, it must be remembered that the reverse process will not occur in an infected plant. The affected area will still turn yellow, and then darken and dry out. But this does not mean at all that the bush will continue to hurt. To be convinced of this, just take a close look at the color of the leaves. The absence of new light green spots indicates that the disease has been suppressed.

Reasons for appearance

The main factor favoring the appearance of late blight is high humidity. If it rains in the summer, late blight begins to spread rapidly. This is a “mass destruction” disease; it affects almost all tomato bushes, leading to very large crop losses.

Other reasons for the spread of late blight:

dense plantings and poor ventilation;
planting next to potatoes - most often they are the first to become infected with late blight;
significant discrepancy between day and night temperatures;
heavy morning dew;
low daytime temperatures;
excessive watering in the second half of summer;
irrigation by sprinkling;
nitrogen overdose;
excess lime in the soil;
lack of manganese, iodine, copper, potassium in the soil.

The fungus that causes late blight can spread by wind, water, and through garden tools.

Preventive measures

In order to protect tomatoes from late blight and preserve the harvest, you need to remember about preventive measures:

The area where peppers, potatoes and eggplants were previously grown cannot be used for planting tomatoes. Also, areas with these crops are not recommended to be located next to each other. In the same area where tomatoes grew, they can be planted again only after at least four years. It is best to grow tomatoes after cucumbers, turnips, carrots, onions, beets and cauliflower.
Tomatoes are grown in a well-lit area.
Experts advise using early varieties or hybrids that are highly resistant to late blight.
If the ground contains an excessively large amount of lime, then during planting, pour a little peat into the hole and put onion peels, and cover the surface of the soil near the bush with sand.
Plants should be well ventilated, so they are not planted too densely.
When watering, pour water only at the roots, and carry out this procedure in the morning. From mid to late summer, watering is recommended only during prolonged drought.
The surface of the soil around the tomatoes is covered with a layer of mulch.
It is recommended to grow calendula, onions, marigolds, white mustard or garlic next to tomatoes.
Carry out stepsoning in a timely manner.
Strengthen the health of plants; for this they are fed with potassium-phosphorus fertilizer, and also treated with immunomodulators.
It is recommended to apply nitrogen only from the beginning to the middle of the growing season. If it is added to the soil in the second half of summer, this will increase the likelihood of bushes being affected by late blight.

Treatment with chemicals

Chemicals are highly effective and are usually used when signs of the disease appear. Their disadvantage is toxicity and the ability to accumulate in soil and fruits.

Fitosporin

This is a biofungicide with antifungal and antibacterial effects. The drug contains Bacillus subtilis, a natural enemy of the pathogen late blight.

Effect of using Fitosporin:

inhibits the spread of late blight;
helps improve soil condition;
the treated leaves and shoots are covered with a protective film that prevents damage by bacteria and fungi.

The drug can be used at different stages - during seed treatment, when transplanting seedlings, during the period of damage. Fitosporin solution is used to treat not only tomato plantations, but also the soil in tomato rows, garden tools, and dry tops collected for placement in a compost pit.

How to use Fitosporin:

after the first treatment, repeat spraying is carried out - about a week later;
It is recommended to water the soil with Fitosporin solution once a month;
For prevention, foliage is sprayed if unfavorable weather conditions arise.

Dosage for spraying – 3 tsp. on a bucket of water. For better adhesion, it is recommended to add 1 tbsp to the solution. l. liquid soap.

Hom

The drug HOM is a fungicide based on copper oxychloride. It is a light green powdery product that is insoluble in water. HOM is part of many combined fungicides - Ordan, Kuprolux, Homoxil and others.

The drug has a preventive and protective effect. It protects plants from fungus from the moment spores germinate until the symptoms of late blight appear. If signs of disease appear on the bushes, spraying with HOM will no longer be enough; a systemic fungicide is additionally needed.

Features of using HOM:

The drug is effective until the disease appears. If the leaves begin to turn brown, it is too late to apply HOM.
It is allowed to use HOM no more than 4 times during the season.
An interval of 10 days should be observed between sprayings. This frequency is justified when there is a high risk of infection and during rainy summers.

How to prepare and use HOM solution:

Dilute 40 g of dry drug or 50 g of suspension in 1 liter of water.
Mix thoroughly and bring the volume to 10 liters.
Spray the bushes with the prepared mixture - 1-1.5 liters for every 10 square meters. m of tomato plantation.
You need to spray the leaves not only from above, but also from below.

The HOM solution should not flow from the bushes into the soil. This can trigger the suppression of beneficial soil fauna, such as earthworms.

HOM is cheap, non-phytotoxic and does not accumulate in fruits and soil. The disadvantages of the drug include a short period of protection, washing off by rain and a large amount of solution that must be prepared for treatment. HOM provokes corrosion of metal products.

Ordan

The powdered domestic drug Ordan is used for the treatment and prevention of late blight and other fungal diseases. Contains copper oxychloride and cymoxanil. The first component has an external effect, the second - internal.

Ordan inhibits and destroys various pathogens, heals infected areas, and has a complex effect. Pathogens do not have resistance to this drug. Ordan is low toxic and is completely removed from the soil during the season.

Features of using Ordan:

the drug is used at all stages of tomato development, except flowering - so as not to poison the bees;
the treatment is not carried out in sunny weather so as not to cause burns;
It is prohibited to treat wet plants;
the maximum number of sprayings per season is 2-3;
Consumption rate in open ground is 80 ml of working solution per 1 sq. m.

How to prepare and use Ordan's solution:

Dilute 50 g of powder in a bucket of water.
Spray the leaves and stems on the day you prepare the solution.

Ridomil Gold

This systemic contact fungicide is made in Switzerland. Contains two active ingredients - mancozeb and mefenoxam, respectively, for external and internal protection. The drug affects a wide range of pathogens and does not allow relapses. It is effective in advanced stages, does not burn, does not freeze, and does not precipitate.

Cons of Ridomil Gold:

expensive;
toxic;
high consumption per 1 sq. m;
accumulates in the ground;
kills beneficial fungi in the soil.

How to prepare and use the solution:

Dilute 50 g of powder in 5 liters of water.
Mix thoroughly.
Add up to 10 liters and spray the beds in the morning - if there is no dew, or in the evening.
Use the prepared solution within 2-3 hours.

Thanos

Thanos is a contact-systemic fungicide intended for the prevention and treatment of fungal diseases. Contains two active ingredients - cymoxanil and famoxadone. The first substance has a triple effect - it treats, prevents and protects, the second - kills fungal spores.

Water-soluble granules do not freeze or crystallize, do not generate dust and are perfectly soluble in water. The drug has a wide spectrum of action, in addition to late blight, it saves tomatoes from phomosis, mildew, various rots and other diseases.

Advantages of Thanos:

combined action;
does not accumulate in fruits and soil;
economical;
fast-acting;
convenient release form.

Thanos has no flaws. The main thing is to follow the dosage and act according to the instructions.

How to prepare the solution:

dissolve the drug according to the dosage indicated on the package;
Pour the mixture into the sprayer tank and add water.

The protection is effective for two weeks. During the season, the drug is used up to 4 times. The minimum intervals between treatments are 15 days. The first spraying is recommended 2 weeks after planting the seedlings.

8 Profit Gold

The drug has a wide range of effects, shows high results in the fight against late blight, gray and white rot, powdery mildew, fomoz, and fungi. Such a high result is achieved thanks to the main ingredients in the composition - famoxadone and cymoxanil. After applying the product, they create a protective shell that prevents the penetration of pathogenic bacteria from the outside. Cymoxanil penetrates deep into the tissues of the microorganism and destroys it from the inside. The most interesting thing is that the protective layer also envelops new branches, preventing them from becoming infected.

Before work, prepare the solution according to the instructions, without exceeding the norms. The granules are diluted with water in the required ratio, for tomatoes and potatoes - 1.5 g per 2.5 liters of water. The finished mixture is poured into a spray bottle and applied to plants by spraying. One package weighing 1.5 g is enough to treat an area of 25 m2. The fungicide begins to act immediately and retains its antibacterial ability until the problem is completely eliminated. The drug is equally effective on different varieties of tomato and potato. It is not afraid of precipitation, it is resistant to washing out. The treatment can be repeated 3-4 times during the growing season.

Traditional methods against late blight

Fans of natural farming successfully replace chemicals with various folk remedies. Their plus is absolute harmlessness to humans, the minus is the need for regular treatments.

Here are some of them:

Salt. The salt solution, falling on the aboveground parts of the plant, covers them with a thin protective layer that prevents the penetration of fungi into the plant tissue. Saline solution is a prophylactic agent that provides only external protection to the plant. Prepare a solution by diluting 250 g of salt in 10 liters of water.
Soda. 1 tbsp. l. dissolve baking soda in a bucket of water. To prevent the solution from dripping from the leaves onto the ground, add liquid soap to it - 1-2 tbsp. l. Thanks to the detergent, the composition will “stick” to the leaves and shoots. Spraying is carried out with a frequency of 1 week, and also after each rain.
Kefir or whey. This method is based on the ability of lactic acid bacteria to suppress fungus and other pathogenic flora. Used for preventive and therapeutic purposes. Dilute whey/kefir in water in a ratio of 1:1/1:10. If you don't have kefir, you can replace it with milk. For 1 liter of milk you need to add 20 drops of iodine and dilute it in the same way as kefir. Milk processing can be done daily.
Ash. Dissolve 5 kg of wood ash in a bucket of water. Leave for 3 days, stirring the ash solution from time to time. Bring the volume to 30 liters, pour in a couple of tablespoons of liquid soap and spray the tomatoes every week.
Hay. The method is based on the ability of Bacillus subtilis to prevent the development of the pathogen. Take 1 kg of rotted hay and fill it with a bucket of warm water. Add 100 g of urea and leave for 3 days.
Hot water. The advantage of the method is its low cost. Bring the water to a boil, cool slightly and pour it into a watering can with a rainfall attachment. Water the soil with hot water so that the water does not get on the plants. Watering frequency – 1 time per week.
Yeast. They are used as follows: dilute 100 g of yeast in 10 liters of warm water. Leave for 1-2 days and spray the bushes.
Vinegar. Dilute 1/2 cup of 9% vinegar in 10 liters of water. Spray the entire above-ground part of the tomatoes. Alternate treatment with vinegar with other folk remedies.
Garlic tincture. Garlic tincture is universal; it simultaneously repels pests and protects plants from bacteria and fungi. Grind the garlic arrows and heads in a meat grinder. Pour 1.5 cups of raw material into a bucket of water and leave for 24 hours. Spray tomatoes once every six months.

How to treat tomatoes against late blight in open ground

To protect tomatoes from late blight, it is important to follow a prevention schedule . This minimizes the likelihood of plant infection:

The first treatment is carried out before the inflorescences appear. Both homemade and chemical preparations are used.
The tomatoes are sprayed a second time after the first ovary appears. It is allowed to use only pharmaceutical or folk remedies.
Then spraying is carried out every two weeks.

This schedule is suitable for the prevention of late blight . If the plants are already sick, treatment is carried out more often.

It is possible to stop the development of late blight in the early stages . To do this, the plants are carefully inspected and the affected leaves are removed. The cut areas are sprinkled with ash.

Bushes with affected stems are removed completely . They are taken off site and burned. After this, healthy plantings are treated weekly. The soil is watered with a solution of potassium permanganate, “Fitosporin” or copper sulfate.

Before treating the soil with anti-phytophthora agents, water the soil with ordinary warm water. This will prevent the roots from rotting.

other methods

Along with fungicides and folk remedies, other methods are also used to combat late blight. The advantages of alternative methods are simplicity, cheapness and efficiency.

Bordeaux mixture

This popular remedy is a mixture of quicklime and copper sulfate. Only the affected parts of the plants are sprayed with the prepared solution. During the season, 4 treatments are carried out. Intervals between spraying are 7-12 days.

How to prepare and use the solution:

Mix 100 g of copper sulfate and 150 g of lime (quicklime) in a bucket of warm water. Follow the sequence of actions - first dissolve the vitriol, then the lime.
Spray tomatoes using protective equipment. The weather should be clear and calm. The optimal time is morning and evening. Consumption rate – 1 liter of solution per 5 square meters. m.

It is forbidden to prepare a solution of Bordeaux mixture in a metal container. It is recommended to use utensils made of plastic, glass or wood.

Copper sulfate

This universal and inexpensive remedy has antimicrobial and antifungal effects and helps against a wide variety of diseases. Practical experience shows that the product effectively prevents late blight.

Benefits of copper sulfate:

suitable for different crops;
kills spores located on plants and in the soil;
is considered a low-hazard substance;
It is partly a fertilizer, as it contains copper, which is necessary for the functioning of cells.

A lack of copper leads to inhibition of the development of tomatoes - their ovaries and fruits do not form, and the leaves turn brown and die.

Dosage, g/10 l:

for soaking seeds – 1;
for spraying bushes – 10;
for soil disinfection – 100.

How to prepare a 1% solution for irrigation:

Dilute 100 g of powder in 1 liter of warm water heated to +40°C.
Make a blue solution in a bucket by adding 9 liters of water.
If the crystals have not completely dissolved, strain the solution through a piece of gauze.
Use the composition within 9 hours. The next day the solution will be ineffective.

Mulching

Mulching is a universal agricultural technique that allows you to achieve several goals at once. You can use peat or compost for mulch.

Mulching effect:

preventing soil drying out;
avoiding excess watering;
protection against fungi living in the soil.

Mulching is especially necessary when planting tomatoes without tying them up, when the bushes are partially in contact with the ground. If you do not add a layer of mulch, the pathogen, climbing the leaves in contact with the soil, penetrates the stem. If this happens, then late blight cannot be stopped. All that remains is to collect the fruits and put them for ripening.

Using Copper Wire

Phytophthora fungi are extremely sensitive to all copper-containing drugs. They are afraid of copper in any shape or form. This is the basis of another method of combating late blight. For this you will need a coil of thin copper wire.

Procedure:

Wrap the wire around the tomato stems at the root collar.
Cut a piece of wire about 3-5 cm long and pierce the stem at the base with it. Bend the ends of the wire to the ground.

This method can only be used for well-developed bushes. Otherwise, you can destroy the plants.

Prevention and treatment

To prevent and treat late blight, various means are used: chemical, pharmaceutical and folk. Most chemicals are toxic to people, so tomatoes are sprayed only before flowering at the first sign of disease. Most plants are already blooming, which means chemicals are not suitable for treatment.

Some preparations are suitable for cultivating the land after harvesting.

Pharmaceutical preparations will not harm the environment and will not cause severe poisoning. They are used as prophylactic agents and medicine at the initial stage of late blight. Gardeners buy trichopolum, furatsilin and boric acid at the pharmacy. Trichopolum and furatsilin are antibacterial drugs that destroy late blight spores. Boric acid is effective due to its acidity, which the fungus cannot tolerate.

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Solutions for processing tomatoes according to folk recipes are easy to prepare yourself from what you have in the house. Treatment with home remedies is possible during the period of ovary formation.

Rules for processing plants

In order for the effect of drugs used against late blight to be maximum, certain rules must be followed:

spraying treatment is carried out only on calm and sunny days;
when using toxic drugs, it is necessary to wear protective equipment;
It is prohibited to prepare chemical and some other solutions in metal containers to avoid oxidation.

Prevention of late blight on tomatoes

Preventive protection of tomatoes from late blight consists primarily of following agricultural practices. Measures to prevent fungal damage to tomato plantings depend on where they are grown - in a greenhouse or in open ground. In both cases, it is necessary to treat the seeds by placing them in a solution of potassium permanganate for 30 minutes before sowing.

In the greenhouse

The greenhouse creates ideal conditions not only for plants, but also for pathogens - fungi, bacteria and other infections. The causative agent of late blight actively develops in humid, stagnant air, which often reigns in greenhouses.

Prevention measures:

If the greenhouse/greenhouse has been in use for more than a year, cleaning and disinfection are necessary.
The room is cleared of cobwebs and plant debris.
The soil in the greenhouse is completely changed.
Disinfection is carried out using different methods. One of the simplest and most effective is fumigation. A metal container filled with smoldering coals is brought into the greenhouse. Woolen fabric is placed on top of them. The room is fumigated for 24 hours. The second option is spraying with disinfectants, Fitosporin or Baikal.
When planting, seedlings are sprinkled with tobacco dust or wood ash.
Ventilate the greenhouse to prevent condensation.

In the open ground

Prevention of late blight in open ground requires an integrated approach. It is necessary to comply with irrigation standards, crop rotation and other rules of agricultural technology.

Prevention measures:

Soil deoxidation by adding lime. To restore normal soil acidity, it is necessary to add peat under digging.
When planting seedlings, dry sand is thrown into each hole - about 3 tbsp. l.
In an area where onions, potatoes, beets, cucumbers or carrots grew, tomatoes are not planted for at least 3 years.
Choose a sunny area for tomatoes, without stagnant water.
Watering - in the morning or late in the evening, at the root. If the summer is humid, watering is canceled.
The soil is regularly loosened to provide air access to the roots.

Prevention of tomato late blight

It is better to prevent any attack than to treat it. To avoid late blight, it is important:

Plant tomatoes resistant to late blight for open ground and greenhouses in appropriate climatic conditions;
Add the necessary microelements to the soil to resist diseases of tomatoes;
Maintain proper watering and re-water the crop;
Grow seedlings according to all the rules, because strong plants are more difficult to kill;
Treat the greenhouse with Fitosporin or Baikal-M;
Make planting sparser to ensure there is enough air and light;
Eliminate weeds as they appear and do not accumulate tops in the compost;
Do preventative spraying.

With proper care of tomatoes and their timely treatment, the putrefactive fungus will definitely not spread. Protecting tomatoes from late blight is a guarantee of a rich and high-quality harvest!

Possible mistakes when fighting late blight

Despite the abundance of means and methods to combat late blight, this disease appears in many gardens every summer. The cause of the disease is often gross mistakes made by gardeners.

Common mistakes:

The use of sprinkling when watering beds. Tomatoes can only be watered at the root. The optimal method of soil moistening is drip irrigation.
Incorrect feeding. In order for tomatoes to successfully resist the late blight pathogen, they must be fed with potassium-phosphorus fertilizers. Do not overuse nitrogen fertilizers.
Watering during illness. If late blight has already appeared on a tomato plantation, watering them is strictly prohibited. High humidity will only enhance the development of pathogens.
Using several methods. You cannot use different methods of struggle at the same time. Combining chemicals is especially harmful. Plants die from an excess of “chemistry”, and their fruits accumulate a critical amount of poisons.

An experienced gardener will tell you how to fight late blight on tomatoes in the following video:

Despite the destructiveness of late blight for tomatoes, it can be successfully combated. There are dozens of simple and effective methods that can not only treat this fungal infection, but also prevent it.

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Useful tips from experienced summer residents

Experienced gardeners know several secrets of combating and preventing late blight. The list contains the most successful of them :

To avoid late blight infecting tomatoes, make sure that the soil around the tomatoes is only slightly moist. To maintain the optimal level of humidity in film shelters, several small holes are made in them.
To protect tomatoes from late blight, some gardeners spray them with a decoction of wormwood, dandelion or celandine. It is useful to add a few drops of iodine to this mixture. This preparation is not only used to spray the bushes, but also to water the soil. It has an antifungal effect and further enriches the soil.
It has been noticed that if you plant wheat, rye, basil or tobacco around the tomato beds and between the rows, the likelihood of them becoming infected with late blight will significantly decrease.