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.

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.

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.

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.

Green manure for the prevention of late blight

Green manure saturates the soil with nitrogen, accumulating it from the air. Other crops will impoverish the garden bed, but these will enrich it. They do not cancel fertilizers. It is still worth using bait. Green manure prevents the conversion of nutrients into forms that are not digestible by plants. They improve air exchange thanks to a developed root system. They actively grow green biomass, which contains many useful substances. This is reliable protection against late blight spores. In particular, white mustard, oilseed radish, rapeseed, and phacelia are used.

Oilseed radish

The root system of oil radish functions in a special way. Substances that are attractive to pseudomonos bacteria accumulate in the soil. These bacteria are found everywhere in the soil. They have a disinfecting effect and prevent the development of the fungus. A symbiotic relationship is formed with radish. All season long, tomatoes will be under reliable protection if this species grows nearby. The likelihood of infection is sharply reduced. The foliage accumulates many essential oils that have disinfectant properties. All this makes it an excellent green fertilizer.

White mustard

Mustard emits an aroma that repels Colorado potato beetles. In addition, it synthesizes phytoncides, strengthening the immunity of tomatoes. Elements necessary to suppress spore activity accumulate in its roots.

Phacelia

Phacelia stops soil acidification reactions, which is generally useful. The level of fertility increases due to the fact that nutrients are transferred into an easily digestible form. This flower has proven itself well as a biofertilizer and is actively used in the USA and European countries. In Russia, the most popular variety is Phacelia tansy. All its subspecies are excellent protection against late blight spores. Experts recommend combining the method of biofertilizers, green manure beds with mulching.

Rape

Another useful plant used as green manure is rapeseed. It also demonstrates antifungal effects. Essential oils accumulate in its leaves and stems, as in oil radish.

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 a greenhouse before the onset of the disease

In order not to be tormented by the question of how to get rid of late blight in a greenhouse, it is worth carrying out preventive treatments in advance.

Photo from rosewoodcreations.com

After planting the seedlings, dust the row spaces with ash. Before flowering begins and during the period when the ovaries appear, repeat the procedure. You can also prepare an ash solution (5 kg per 10 liters of water, then increase to 30 liters) and spray the plants with it 3 times per season.

During the growing season, spray the plantings with Abiga-Peak, Consento, Revus or other fungicidal preparations according to the instructions. Repeat the procedure every 15-20 days. Such preventive treatment of tomatoes against late blight will help prevent the onset of the disease. Just remember to use personal protective equipment when spraying and do not exceed the drug limits. To prepare solutions, use any utensils except metal ones, because... it reacts chemically with the components of the drugs and can reduce their effectiveness.

The best time for spraying is morning or evening.

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.

The best varieties of tomatoes for the greenhouse, resistant to late blight

There are no varieties and hybrids of tomatoes that are absolutely not susceptible to the disease. But every year more and more varieties appear that are more resistant to late blight than others. For example:

Oak is a determinate variety with a compact bush. Characterized by early ripening (85-100 days). Unpretentious and frost-resistant. The fruits are small, weighing up to 100 g, collected in a cluster, and have a good taste. Tomatoes are particularly resistant to late blight.
Orange miracle is an early ripening determinate variety of tomatoes. Ripening period is up to 100 days. The fruits are large (up to 150 g), pear-shaped, orange in color, a high-yielding variety. Due to their high beta-carotene content, they are very useful. The taste is excellent, the sweetish fruits are suitable for fresh consumption.
Lark is a hybrid variety of determinate species, bush height up to 90 cm. Ultra-early ripening (80 days after germination), fruits 100-120 g. Excellent, sweetish taste, bright red color, used for salads and canning. The hybrid is able to set fruit even in unfavorable conditions.
De Barao is an indeterminate variety. Despite the late ripening of tomatoes (115-120 days), it has strong immunity against late blight. Plants are tall - up to 2 meters; formation and pinching of tomatoes is required. The fruits are plum-shaped, there are varieties with red, yellow, black fruits, weighing 70-90 g, universal use.
Cardinal is a mid-season indeterminate variety, up to 2 m high. Ripening time is 110-115 days. Large fruits weighing 400-900 g; up to 10 tomatoes can form on one cluster. The variety is high-yielding, cold-resistant, the fruits are fleshy and have an excellent taste. They are distinguished by high keeping quality and do not crack.
Gardeners note that late blight is a serious disease that can destroy most of the crop, so it is easier to prevent than to treat.

Carrying out preventive measures and alternating different methods of combating the disease will help preserve the plants and get an excellent harvest of tomatoes.

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.

Preventive measures

To reduce the occurrence of late blight on the site, it is advisable to use the prevention of this disease:

Correct landing. Tomatoes should not be planted in the place where potatoes, peppers, and eggplants previously grew, and these crops should not be located nearby. An ideal place for tomatoes is the bed where cucumbers, beets, onions, etc. previously grew. It is best to plant tomatoes in a new location every year.
It is recommended to dilute soil with a high lime content with peat (it is added to the planting hole), and after planting, a small amount of sand is poured next to the bushes.
Tomatoes need to be planted maintaining the distance between the bushes and avoiding thickening of the plantings.
Watering should be at the roots, water should not get on the foliage and tomatoes. It is important not to forget about loosening the soil layer next to the bushes.
Carrying out mulching.
It is recommended to plant white mustard, calendula, marigolds, garlic and onions near tomatoes.
Timely pinching and cutting off unnecessary leaves.
Applying potassium and phosphorus fertilizers, spraying with immunostimulating substances to enhance the plant’s immune system.
Regular ventilation of the greenhouse.
Application of nitrogen fertilizers in the first half of the growing season, then excess nitrogen can provoke the appearance of late blight.

Following these simple rules will prevent tomatoes from becoming infected with a dangerous disease. Every gardener must remember that it is easier to prevent any illness than to treat it later.

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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How to prevent relapses of late blight

The following recommendations will help you avoid re-infection with a fungal disease:

observe crop rotation (change plots every 4-5 years);
avoid crowding of plants;
tear off the lower leaves of tomatoes before the first ovary for better ventilation and more light flow;
do not create a compost heap in the garden;
remove nightshade tops from the site and destroy them;
water the plants strictly at the roots;
when growing indoors, ventilate the greenhouse;
Do not use fresh manure as fertilizer.

After planting in a permanent place, it is recommended to treat with biological fungicides for preventive purposes. Fitosporin M for tomatoes has proven itself to be such a product.