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How to protect the tomato harvest from late blight

How to protect the tomato harvest from late blight


Tomatoes are a rather delicate crop that is prone to a huge number of diseases. Cladosporium, apical rot, septoria, gray rot, brown rot, root rot, mosaic - these are just some of the ailments. But, perhaps, the most common is still late blight or late blight. You should not be afraid of phytophthora on tomatoes, because there are a number of preventive measures that will help protect your plant.

Phytophthora - what is it?

Phytophthora is the most common disease affecting nightshade crops. This fungal culture is equally dangerous for such members of the family as eggplant, potatoes, physalis, peppers and, of course, tomato. The disease appears quite often, instilling terror in every gardener, because the whole crop can die as a result. Often people do not know exactly how to deal with this ailment and what preventive measures should be taken. To understand and develop an action plan, you first need to figure out exactly how and for what reasons late blight appears.

There are a fairly large number of factors affecting its appearance, here are the main ones:

  • planting different plants of the same crop (in this case nightshade) close to each other. As stated earlier, potatoes and eggplant are also at risk. The fungal disease is easily transmitted from bush to bush;
  • insufficient pinning or its absence. Phytophthora may appear due to insufficient ventilation. Therefore, it is necessary to pinch tomato bushes, especially those that reach maximum height and, growing, receive less and less air;
  • important for the harmonious growth of the tomato is the observance of the temperature regime. Often, at the end of summer, in August, the nights get colder. A knocked down habitual regime is also the cause of the appearance of a fungus;
  • the reproduction of the phytophthora fungus is provided by climatic conditions such as rain, as well as cold. Therefore, if you want to get a harvest, you should think in advance about building greenhouses;
  • often inexperienced gardeners who are just learning how to properly care for plants water the tomatoes directly on the leaves. It is strictly forbidden to do this, since excess moisture creates a comfortable environment for the fungal culture.

Thus, the main cause of late blight in tomatoes is, of course, excess moisture. Like any fungus, late blight loves secluded, humid and poorly ventilated places. Tomatoes grown in a greenhouse are almost completely protected due to the following factors:

  1. compliance with the temperature regime;
  2. watering is strictly regulated, there is no additional uncontrolled humidification (rains);
  3. constant ventilation controls the level of air humidity;
  4. the film protects tomatoes from the spread of fungus from other plants in the culture.

Now that the factors causing the disease are known, we can talk about how exactly to distinguish this particular disease from others.

Manifestation of the disease

Potatoes are the first of the nightshades to be affected by late blight. Therefore, experienced gardeners always control this crop in order to reduce the risks of diseases of other plants. To do this, it is necessary not only to conduct a thorough examination, but also to remove all suspicious leaves from the tops of the potatoes, because they may indicate the beginning of the process of fungal infection.
Basically, they cut off the leaves that are almost at the ground.

The parasitic action of phytophthora affects mainly adult plants.

  • First of all, you need to pay attention to the leaves of the bush. Irregular brown spots appear on them, as well as a white fluffy bloom. This plaque is the focus of the formation of spores, which are carried by the wind to other plants.
  • most often, the fungus begins its destructive effect from the lower leaves, which are closest to the soil, and therefore suffer more than others from waterlogging. Especially carefully you need to check the edges - it is there that moisture collects;
  • over time, inflorescences acquire black color, sepals dry up, peduncles disappear;
  • the stems are also affected with brown spots of an elongated shape, but without plaque. Over time, spots can merge into one;
  • the fruits begin to rot, affected by brown spots that form under the skin of the tomatoes. Over time, the spots completely affect the entire fetus.

Fight against late blight

To begin with, it is necessary to consider the control measures that warn against late blight on tomatoes. Prevention should be started much earlier than the growing season - during the off-season. After the entire crop has been harvested, the area must be carefully cleaned of any organic debris. They can be buried in a cesspool, or completely removed from the site. The harvested soil must be dug to a depth of about twenty centimeters. If the crop was harvested in a greenhouse, then it is necessary to renew the top layer of the soil, as well as to process the greenhouse with chloride lime.

It is important to observe the crop rotation. This means that the tomato is recommended to be returned to the same land only four years later. It is necessary to choose the soil for a new planting understanding the peculiarities of this culture.

Tomatoes should be planted in an area that is well warmed by the sun and where there is no stagnant air. Statistics say that 90% of tomatoes growing in the shade are infected with this fungus.

Removing weeds will provide "breathing" to the lower leaves of the plant, protect them from waterlogging. It is also useful to remove the lower leaves. Be sure to follow the watering schedule, in rainy or cloudy weather it is better to cancel watering. The best watering is in the evening.

There are also a number of precautions for those whose landing area is often prone to late blight of tomatoes. First, it is worth choosing tomato varieties that are more or less protected from disease. Secondly, before planting seedlings, you can process it with 0.5% Bordeaux liquid - a solution of copper sulfate diluted in milk of lime. After one and a half to two weeks, repeat the treatment with a 1% solution. There are also other methods of treating with chemicals: copper chloride (40 g per 10 liters), watering with an ash solution or sprinkling ash directly on the ground.

Now we move on to the growing season. What drugs will help us during this period? Basically, various fungicides are used to combat the fungus. They should be based on copper. The most common on the market and available to the consumer are copper sulfate and, previously indicated, Bordeaux liquid. So, the methods of spraying during the growing season:

  • copper-soap solution (2 g of copper sulfate + 200 g of soap + 10 l of water). The whole plant is sprayed with this emulsion. The first time during fruit setting, then after 8-10 days;
  • 30 g of potassium chloride + 40 drops of iodine + 10 liters of water. Watering at the rate of 0.5 liters per bush;
  • you can also use purchased ready-made drugs: "Oxychoma", "Quadris", "Infinito", "Hom". In stores you can find other drugs - fungicides, they differ little from each other and are equally effective in the fight against late blight of tomatoes.

Preventing plant disease is easier than dealing with it and its consequences. Therefore, having carefully studied the information on the nature of late blight of tomatoes, as well as preventive measures in the fight against this fungus, even an inexperienced gardener can easily protect his harvest, and also preserve the health of the soil and other crops planted nearby.

Video "Processing of tomato from late blight"

This entry shows when and how to chemically treat tomatoes outdoors to avoid late blight.


Late blight: fight and treatment, remedies for late blight

Author: Natalya Category: Plant Diseases Published: February 28, 2019 Last revised: July 16, 2020

  • Listen to the article
  • Late blight (late blight) - description
  • Fight against late blight
    • Protection against late blight (late blight)
    • Treatment for late blight
    • Soil treatment from late blight
  • Phytophthora on tomatoes - how to fight
    • Prevention of late blight on tomatoes
    • Phytophthora on tomato seedlings
    • How to treat tomatoes from phytophthora
    • Remedies for late blight on tomatoes
  • Potato late blight
    • Phytophthora on potatoes - processing
    • Prevention of potato late blight
  • Phytophthora in different cultures
  • Preparations for phytophthora
  • Folk remedies for phytophthora
    • Copper wire from late blight
    • Iodine from phytophthora
    • Phytophthora serum
    • Kefir against phytophthora
    • Saline solution for phytophthora
    • Garlic against late blight
    • Ash spraying from late blight
    • Polypore spraying from late blight
  • Literature
  • Comments (1)

Phytophthora (Latin Phytophthora) - a genus of mushroom-like microorganisms that cause late blight disease in plants. More than seventy types of phytophthora have been described, but, according to experts, there are up to five hundred varieties that have not yet been described. The name "late blight" consists of two Greek words that mean "plant" and "destroy". Late blight primarily affects nightshade crops - potatoes, tomatoes, eggplants and peppers.


Where can it come from?

When planting beautiful and healthy tomato seedlings in a greenhouse, you need to know that this does not guarantee a good harvest. For several years, a fungal infection has been living in the ground - late blight., she may not show herself in any way. Only under certain conditions in the greenhouse there is a reproduction of this type of fungus and the defeat of tomatoes.

It should also be borne in mind that fungal spores can be brought in with a tool, on clothes, with seedling soil, wind, etc. Late blight tends to change and mutate, which complicates the fight against this fungus.

In the photo you will see what a dangerous disease that affects greenhouse tomatoes looks like:





Prevention of phytophthora. Main events

  1. Phytophtora loves thickening. Therefore, regularly remove stepchildren from tomatoes, as well as the lower leaves up to the first flower brush.
  2. Ventilate the greenhouse, make sure that the air in it is dry, as the formation of condensation on the film and the ingress of drops on the leaves lead to the rapid spread of the disease.
  3. Feed the tomatoes with phosphorus and potassium fertilizers during the formation of fruits - this helps to strengthen their immunity.
  4. Do a preventive spraying every 7-10 days. At the beginning of the season, chemical preparations are acceptable: Penncoceb, Ridomil - according to the instructions.
  5. With the advent of small fruit set, it is better to use folk remedies for treatments:
  • 1 liter of fermented kefir per 10 liters of water
  • pour half a bucket of wood ash with 10 liters of water, insist for three days, stirring occasionally. Drain the settled liquid, bring the volume to 30 liters and add 30-35 ml of liquid soap

  • at the first signs of phytophthora, plants can be watered with a yeast solution (80 g per bucket of water)
  • iodine-milk "cocktail" helps: 1 liter of milk and 20 drops of iodine per 10 liters of water.
    Yanina GORBATENKO, agronomist, Mogilev.


Causes of the disease

Before starting an effective fight against late blight, it is worth knowing what are the causes of the disease. Consider the main ones that cause late blight on tomatoes:

  • Close proximity to potatoes (more often the disease begins with it)
  • Dense plantings and lack of ventilation between the bushes
  • A large difference between night and daytime temperatures and heavy dew in the morning (more often this occurs in August), as well as a lack of heat
  • Frequent and heavy rains in the second half of summer
  • Excessive watering in July-August during fruit ripening, as well as irrigation on the leaves
  • Excess nitrogen
  • Increased lime content in the soil
  • Lack of potassium, copper, iodine, manganese in the soil.

Knowing the main reasons, you can avoid mistakes in care in advance and save your crop.


To prevent the spread of phytophthora spores and protect tomatoes, it is recommended to follow preventive measures:

  1. Autumn processing of greenhouses with sulfur checkers.
  2. Spring disinfection of soil with copper sulfate.
  3. Controlling soil nitrogen levels and restoring natural balance with peat and coarse sand.
  4. Moderate watering.
  5. Frequent loosening of the soil.
  6. Stealing and thinning.
  7. Soil mulching with sawdust and pine needles.
  8. Airing greenhouses.
  9. Shelter of beds in open ground with spunbond (agrofibre made of environmentally friendly polypropylene).
  10. Timely introduction of potassium-phosphorus dressings.
  11. Compliance with the principles of crop rotation (the best predecessors of tomatoes are white cabbage and cauliflower, zucchini, legumes, pumpkin, onions).
  12. Soaking the seeds collected by hand in a solution of "Fitosporin" or "Phytodoctor".
  13. Treatment of wells for seedlings with boiling water or a hot solution of potassium permanganate.


Prevention of late blight on tomatoes

Protection of tomatoes from late blight

It is no secret for any gardener that it is better to prevent disease than to fight it, even if it is successful. In order to protect tomatoes from late blight infection, there are effective preventive measures. How to spray tomatoes from late blight? What preventive measures can protect them from infection?

In the photo: Tomato late blight disease

Prevention of late blight on tomatoes in the open field

Dissolve a glass of cooking salt in 10 liters of water and treat poured, but still green tomatoes with this brine - the composition forms a film on the fruits that protects them from infection.

You can dilute 1 liter of kefir in 10 liters of water, fermented for two days, mix thoroughly and process the tomatoes with this composition. The first spraying should be carried out two weeks after planting the seedlings in the ground, and then repeat the processing of tomatoes with kefir weekly.

  • Agrotechnical methods of prevention against late blight

    Subject to agricultural practices, you can reliably protect your tomatoes from late blight. Here is a list of activities that serve this purpose:

    • in areas with excessive lime content, the natural balance of the soil should be restored by introducing peat for digging. When planting seedlings, it is better to fill the holes with sand
    • observe the crop rotation: do not plant tomatoes in an area where carrots, turnips, cauliflowers, beets, cucumbers or onions grew before them
    • do not thicken the planting - follow the planting scheme developed by agricultural technicians
    • water the tomatoes in the early morning or after sunset, trying to pour the water so that drops of water do not fall on the plants
    • during a period of high humidity, tomatoes can not be watered at all, but it is very important during this period of time to loosen the soil between the rows
    • feed tomatoes with phosphorus, potassium and other beneficial elements that help strengthen plant immunity - strong, healthy tomatoes are not affected by fungal infections.

    In the photo: Phytophthora on a tomato

    Prevention of late blight on tomatoes in a greenhouse

    Phytophthora on tomatoes in a greenhouse is almost a more frequent visitor than on the beds in the garden. Prevention of late blight in the greenhouse should be started with disinfecting the room. Before planting seedlings, sanitize the greenhouse: wash off dirt, cobwebs, remove plant residues.

    To disinfect the greenhouse, you can use fumigation: put a piece of clean wool in a bucket with burning coals, place the bucket in the greenhouse and close all windows and doors tightly for a day.

    As a preventive treatment of the entire greenhouse and tomatoes, dusting with a mixture of wood ash and tobacco dust is used at the rate of 2 glasses of dust per bucket of ash. Do not forget to wear a mask and glasses before such treatment.

    Instead of tobacco ash powder, you can use a solution of Baikal EM, Radiance or Fitosporin to treat the room in accordance with the manufacturer's instructions.

    In greenhouse conditions, it is better to use drip irrigation to moisten the soil by connecting a special hose to a container with warm water in order to gradually saturate the soil with moisture throughout the day.

    In the photo: Rotting tomatoes due to late blight

    Remember to regularly ventilate the greenhouse and do not allow a large amount of condensation to accumulate in the plastic greenhouse.

    As for the preventive processing of tomatoes directly, in the greenhouse it is carried out at the same stages as in the garden: a week after planting in the ground, before flowering and before the appearance of the first ovaries. If you do everything right, these measures will be enough so that you never see the symptoms of late blight on your tomatoes.

    If phytophthora nevertheless got to your tomato garden, tune in to a long and stubborn struggle - phytophthora just doesn't give up.


    Watch the video: Lesson 2: Early Blight Vs Late Blight