Late blight, septoria, mycoses, bacterial canker, bacterial black spot: how to deal with tomato diseases. Pathogenic lesions on the leaves of tomato seedlings A few words about the disease

The possibility of tomato infection by a pathogen exists throughout the entire growing period. When seedlings are damaged, further development is hampered and the plants have a depressed appearance.

The disease manifests itself locally. On leaf blades, leaf petioles, and stems, small, up to 3 mm, watery, almost black, irregularly shaped spots develop, which are limited by a narrow chlorotic halo.

On young leaves, spots are subject to necrosis, with simultaneous perforation of the center. At times, the spots merge and spread to the vein area. Severely damaged leaves quickly change color to yellow and fall off.

Specific signs of exposure to bacterial black spot are the appearance of dark spots with a watery halo on green fruits. As the infection progresses, they grow and become depressed. The epidermis along the periphery of the spots cracks, and they turn into scabs. Tissues in the immediate vicinity of damage become watery, and rot penetrates deeply into them.

Morphology

The causative agent of the disease is an aerobic, gram-negative bacterium. It is represented by mobile monotrichial capsule-forming rods, 0.6-0.7x1.0-1.5 microns in size.

On rainfed soil, the bacterium forms yellow, round, slimy, shiny, smooth colonies with smooth edges.

In addition to tomatoes, the pathogen affects peppers. Moreover, it is divided into three pathotypes: pepper, tomato and pepper-tomato. The tomato pathotype is differentiated into three races.

Biology

The main sources of infection are the remains of diseased plants and seeds. The pathogen persists in stems and roots until they are completely decomposed. Directly in the soil, outside of plant residues, the bacteria lose their viability within a few days.

The bacterium is transmitted by the seeds of tomatoes and weeds. The possibility of its resistant development on a wide range of weeds and asymptomatically or epiphytically on tomatoes is noted.

Bacteria remain viable on seeds for 1.5 years. It is in this way that the infection spreads to new areas. The pathogen cannot penetrate inside the seeds and survives only on their surface.

In young fruits, up to 2.5 cm in diameter, the infection penetrates through mechanical damage, and into leaves through stomata or damaged hairs of the epidermis of fruits and leaves. Bacteria quickly spread throughout the intercellular spaces. The incubation period lasts three to six days on leaves and five to six days on fruits.

The spread and development of the disease on tomatoes depends on the timing of planting seedlings in open ground. The later the seedlings are planted, the more intense the infection develops. The optimal temperature for colony growth is +25°C-+30°C. Death is observed at +56°C. The pathogen is noted to be resistant to low temperatures and drying.

Intensive development of the disease is observed in cold and damp conditions. Dry and hot weather limits the development of the disease. The impact of infection is especially dangerous during the period of intensive fruit growth. Mature people are not affected.

There are a lot of known diseases in tomatoes. Knowledge about them will be useful to everyone who grows tomatoes to get a tasty, healthy, and generous harvest. Today we will look at the most common tomato diseases that you may encounter.

Bacterial diseases of tomatoes: symptoms, control methods

The causes of bacterial diseases in tomatoes are various bacterioses, leading to the death of plants, a decrease in their fertility and the quality of tomato fruits. Tomato infection by bacteria is much less common than by viruses and fungi.

The disease affects leaves, much less often fruits and stems, and is easily distinguished from other tomato diseases visually. At first, the leaves become covered with oily spots, which over time become dark brown. The diameter of these spots is approximately 2-3 mm. As a result, the leaves curl and die. A satisfactory environment for the development of bacterial mottling is low temperature and high humidity. Pathogenic fungi can persist on seeds and on the roots of accompanying weeds; they can only remain free in the soil for a short time. This disease is quite rare; when it occurs, it is necessary to treat the plants with copper-containing fungicides and Fitolavin-300.

This is a very harmful bacterial disease that affects the entire plant. First the leaves wither. On the petioles, breeding grounds for bacteria are visible - brown growths. The empty yellow core is clearly visible on the cut stem. The fruits spoil both outside and inside. White spots form on the outside of tomato fruits, and inside the bacteria affect the seeds: they are either underdeveloped or will have poor germination. This infection persists on seeds, in soil and on plant debris if tomatoes are grown as a monoculture. To prevent your tomatoes from being overcome by a disease such as bacterial canker, the seeds are soaked in a TMTD suspension on the day of planting, and during the growing season the plants are sprayed with copper-containing fungicides.

Important! Treatment with such preparations is done only in dry and warm weather, so that the tomato bushes are dry.

If your tomato bushes begin to wilt, this is the first outward sign of bacterial wilt. Signs of wilting can appear even overnight; everything happens very quickly, and in such cases there is no talk of a lack of moisture. If you examine the dead plant in detail, you can note the presence of liquid inside the stem and emptiness, and the internal tissues of the stem acquire a brown tint. This disease is almost impossible to cure. Affected plants will have to be destroyed, and all other plants, still without signs of the disease, are recommended to be watered with a 0.6-1% solution of Fitolavin-300 (at least 200 ml for each plant) in order to delay the infection of healthy bushes.

One of the rare diseases of tomatoes. Plant roots become covered with small growths, and bacteria accumulate inside them. The disease is identified thanks to indicator plants (for example, pea seedlings, Kalanchoe). From the moment the infection enters the plant’s body until the first signs appear, approximately 10-12 days pass. The main breeding ground for the disease is affected plants and soil. To avoid tomato root cancer, you must try to minimally injure the roots of the tomatoes, because the causative agent of the disease can only penetrate through fresh wounds. One of the methods of combating root canker is steaming the soil, since steaming kills the pathogen. Also effective will be soaking the roots of tomato seedlings in a solution of Fitosporin-M (2-3.2 g per 1 liter of water).

Wet rot is practically harmless to greenhouse tomatoes and is rarely encountered in practice, but it causes significant damage to tomatoes in open ground. Fruits can contract this disease if there are minor, minor damage. Diseased fruits soften, turn brown, and after a few days they completely rot, and only the skin remains of the fruit. Bacteria of this disease develop well at high humidity, temperature changes and temperatures of +30ºС. Infection is spread by insects and from other infected plants.

Important!Those varieties and hybrids of tomatoes that have a generative growth gene are resistant to wet rot disease.

The main method of combating wet rot in the field is the destruction of insect vectors.

A bacterial disease that is quite serious. The stems of well-developed plants are the first to suffer from necrosis during the formation of the first clusters with fruits. The stems become covered with brown spots that crack after a while, the leaves wither and the plant dies, but the fruits do not have time to ripen. The primary source of this infection is infected seeds, as well as soil and infected plants. The maximum temperature for pathogen growth is 26 – 28ºС, and at 41ºС the bacteria die. Bushes infected with necrosis need to be pulled out (preferably burned), and the soil treated with a 0.2% solution of Fitolavin-300.

This disease can destroy up to 50% of the crop, and the remaining fruits lose their presentation and properties. Plants that are sick with such bacteria appear underdeveloped and weakened. The spots are based on all organs of tomatoes, except for the roots. The spots turn black over time, and the disease progresses even more. Low temperatures are not dangerous for these bacteria, but they die at +56ºС. The infection is transmitted by contaminated seeds and plant debris. It is imperative to treat the seeds, because bacteria on the seeds can live for one and a half years. Treat the seeds with Fitolavin-300. It is also recommended to treat plants (three to four weeks after germination, at intervals of 10-14 days) with 1% Bordeaux mixture and Kartotsid.

Interesting! In France in the 14th century, tomatoes were called “apples of love”, in Germany “apples of paradise”, and in England they were considered poisonous.

Tomato viral diseases: symptoms and methods of control

Viral diseases of tomatoes are caused by various pathogens (viruses) and are dangerous both for the plants themselves and for the future harvest.

Aspermia (spermlessness)

Visually, aspermia can be determined by the high bushiness of the plant, by underdeveloped generative organs and by a weak stem. Tomato flowers grow together, leaves become small and change color. Aspermia is transmitted by insects or through reservoir plants. It affects nightshade crops, asteraceae and others. To prevent aspermia from spreading, you need to remove the reservoir plants and poison the insect carriers.

The bronzing virus is becoming more harmful every year, and it can kill the entire crop. Plants in film greenhouses and in open ground suffer the most from it. Bronzeness on tomatoes is determined by ring patterns on young fruits, which gradually turn brown. Subsequently, the same spots are visible on the leaves of tomatoes. The tops may also die off from time to time. The disease is spread by thrips or mechanically. This virus cannot be treated, but it is inactivated at a temperature of +45ºС. The decisive methods for combating bronzing are the destruction of thrips and the removal of weeds.

The carriers of this disease are whiteflies. Those plants that are affected by the disease at the beginning of the growing season look stunted, the leaves are chlorotic, deformed and small, the plants are unevenly colored. Severely affected plants usually do not set fruit. As for control methods, it is best to plant resistant varieties of tomatoes, destroy weeds, and treat plants with mineral oil to reduce the spread of the disease.

This virus is potentially dangerous and is transmitted through seeds, aphids and mechanically. Its initial symptoms begin to appear in winter. First of all, white spots form on the leaves, and then they begin to acquire a dark brown color and cause necrosis. The leaf plates are rolled down and stretched. After some time, the lower leaves of the plants curl away from the stem at an acute angle. Spindle-shaped plants affected by this virus are stunted in growth, leaf veins begin to turn blue, and the leaf itself becomes rough. The virus dies at a temperature of +75ºС. There are no chemical or biological agents to protect against bushy tops yet. Only agromechanical treatments are carried out. It is recommended to cull diseased seedlings in the early stages, and diseased plants during the growing season.

Mosaic is one of the viral, rather unpleasant, diseases that mainly affects tomatoes grown in open ground. About 10-14% of the crop is destroyed by mosaic. L The leaves of tomatoes that are sick become covered with a variegated (mosaic) color, with alternating dark and light green areas. Yellow spots may sometimes develop on fruits. The first source of this infection is infected seeds. Therefore, for preventive purposes, it is best to treat the seeds before planting, but if the tomatoes still get this infection, then simply remove them.

The causative agent of this disease leads to deformation of plants and drying out of the top. The crop, when infected with the virus, dies almost completely. Diseased leaves have a thread-like and fern-like appearance. The disease spreads through reservoir plants, of which there are a lot, and with the help of aphids. As for protective measures, they are mainly agrotechnical.

Did you know? Tomatoes account for 93% of home gardens in America. This is the most popular vegetable there.

Fungal diseases of tomatoes: symptoms, control methods

Fungal diseases of tomatoes are the most common. Their main feature is that they can affect absolutely any part of tomatoes and are almost untreatable.

Alternaria blight is a fungal disease that affects the stems, leaves and, less commonly, fruits of tomatoes. Initially, the lower leaves succumb to the disease and become covered with large round brown spots with concentric zoning. These spots gradually increase in size and the tomato leaves dry out. The stems are covered with dark brown oval large spots with the same zonation, which lead to dry rot or death of the stem. Slightly depressed dark spots form on the fruits, often near the stalk, and when there is an excess of moisture, dark velvety sporulations of the fungus appear on these spots.

This disease is stimulated by high temperatures (25-30°C). For the purpose of prevention, at the first manifestations of the disease on tomatoes, you need to treat them with antifungal copper-containing agents (Skor, Ridomil Gold, and others); If the disease appears when the fruits are already hanging, it is advisable to treat them with biological products.

There are two types of anthracnose in tomatoes - fruit and leaf. Its harmfulness will be determined by the growing conditions. The disease spreads widely in film greenhouses, and no less in open ground. Anthracnose of tomato leaves most often affects adult plants. First, the upper leaves wither, while the central stem is exposed, maceration of the roots occurs, and the plant is easily pulled out of the ground. The affected parts of the plant are covered with small black sclerotia.

As for anthracnose of fruits, the fruits become covered with depressed dark spots, and, as a result, there may even be mummification of the fruits. To prevent anthracnose, it is recommended to treat the seeds with Agat-25, and during the growing season of plants, spray them with Quadris and Strobi; Preparations based on Bacillus subtilis are also very effective.

White spot (septoria)

About half of the crop can die from septoria. In most cases, old leaves close to the ground are affected. Various spots form on them, they turn brown, become deformed and dry out. White spotting develops best at temperatures from +15ºС to +27ºС and air humidity from 77%. The fungus persists in plant debris. Septoria can be combated by removing plant debris, spraying infected plants with fungicides, maintaining crop rotation and spatial isolation between tomatoes and other nightshade crops.

White rot on tomatoes is often observed during storage. The fruits are covered with wet putrefactive spots. Almost always, this disease forms in places where tomatoes have been mechanically damaged. Actually, white rot develops best in ruptures in fetal tissue. Soil and compost are the primary sources of infection. That is why steaming them is simply necessary for prevention. The main source of infection is sclerotia in the soil, and in order to protect tomatoes from white rot, qualitative disinfection is needed after the previous crop rotation.

Brown spot (cladosporiosis)

Tomato varieties and their hybrids that are more resistant to cladosporiosis are increasingly being developed, and the harm from it is decreasing. Orange spots appear on the lower leaves of plants that are not resistant to this disease, darkening over time. After some time, a dark coating forms on these spots. Brown spot can be stored in greenhouses for up to ten years. The ideal conditions for this are high temperature and humidity. The best way to combat brown spot is to use resistant tomato varieties(for example, Yvon, Cunero, Raisa and others). And when an infection occurs, spray the plants with Abiga-Peak, Polyram and HOM.

Today, verticillium does not cause major damage. The initial signs of the disease can be seen on old leaves - the appearance of chlorosis and necrosis on them. The root system is also gradually being torn away. Since the disease is dual in nature, for one half of the pathogens the ideal temperature is below +25ºС, and for the other - above. Verticillium fungi can be stored in plant debris and soil. The main methods for preventing the disease: pulling out plant debris and growing resistant varieties of tomatoes and hybrids, because there are no fungicides to combat verticillium.

Root rot is possible in open ground in tomato planting areas that are waterlogged, and in greenhouses when growing tomatoes on a substrate. There are relatively few losses. Signs of root rot are blackening near the root collar and root (black leg). Following this, the plant withers. The best circumstances for the spread of the disease are unsterile soil and excessive watering. This proves that the sources of the disease are soil and substrate; sometimes the fungus remains on the seeds. The optimal method of combating root rot is disinfection of the substrate, soil, seedlings and seed dressing.

Important! A very effective way is to loosen the soil and sprinkle the surface of the ground with seedlings with coarse river sand.

Powdery mildew causes the most damage in glass greenhouses, but recently its prevalence has been decreasing. But if your tomatoes are still infected with this disease, then the yield losses can be simply enormous. Powdery mildew in tomatoes is determined as follows: a white coating is created on the leaf blades, the petioles and stems rarely change. Favorable conditions - low temperature and humidity, insufficient watering. To escape from the fungus, plants are sprayed with a solution containing fungicides.(Strobe, Quadris, Topaz and others). Sodium humate 0.01 and 0.1% kills the fungus completely.

A very dangerous fungal disease of tomatoes that kills half the crop, or even more. The fungus gradually overcomes the entire stem, tissue necrosis develops. A whitish-grayish coating becomes visible on the plant, and it steadily withers. Excess air humidity also affects the generative organs. The infection is transmitted to tomatoes and from other crops (for example, cucumbers). As for tomato varieties or their hybrids resistant to this disease, they have not yet been bred. It is necessary to apply agrotechnical measures, growth regulators and chemical methods of protection (Bayleton, Euparen Multi) in a timely manner.

The disease causes different harm to tomatoes, it all depends on where they grow. In glass structures, stem cancer practically does not spread, but in film greenhouses, the entire plant dies from it. In open ground, ascochyta blight is very rare. Ascochyta blight affects tomato stems and sometimes leaves. Brown sunken spots form on the stems and gum oozes from them. The flowers are underdeveloped, the fruits may be covered with the same spots. The disease can persist on seeds and plant debris. Ideal conditions for the development of ascochyta blight are wet and cold weather, low temperature. Methods of fighting infection are disinfecting the soil, adding Trichodermin to it, spraying plants with growth regulators (Immunocytophyte, Agat-25), treating stains with a special paste of chalk and Rovral.

Fusarium blight is quite harmful to tomatoes. First, chlorosis occurs on the lower leaves, and then on all the others. Tomato shoots wilt, petioles and leaf blades become deformed. Those conditions that are not comfortable for plants are simply ideal for the development of such an infection. Tomato plants can pick up this disease from seeds, soil and harvest residues. To prevent the development of Fusarium wilt, resistant tomato varieties are planted(Rhapsody, Raisa, Soret, Monica, and others), before planting, the plants are watered with Pseudobacterin-2 (per plant - 100 ml of the drug). Benzimidazole drugs are also used.

This disease has a low degree of danger. First, the root collar becomes deformed and turns black, which means the plant begins to rot. Then the disease rises up the stem, and it is covered with a white coating of mycelium. Dark spots may also form on tomato fruits, and diseased fruits simply fall off. For the purpose of prevention, the soil is sterilized and infected parts of the plant are removed. Also, for treatment when planting tomatoes, Pseudobacterin-2 is used, and after planting, a 0.01% solution of sodium humate is used.

Interesting! 94.5% of the weight of a tomato is water.

Non-infectious diseases of tomatoes: symptoms and methods of control

Non-infectious diseases of tomatoes can be caused by unfavorable weather conditions and violation of the growing regime.

The disease can occur due to genetic and agrotechnological factors. Green fruits are covered with white or brown spots. Sometimes necrosis affects a third of the tomato fruit, and then the spots turn black. In most cases, blossom end rot is characteristic of large tomato fruits, and its appearance is possible due to a lack of calcium ions, due to the characteristic concentration of the soil solution, when pH is less than 6, at elevated temperatures, etc.

To prevent the appearance of blossom end rot, be sure to water the plants on time so that the soil does not dry out and rot, use foliar fertilizing with special preparations, and use fertilizers that contain calcium before planting. You can also plant varieties and hybrids resistant to this disease.

Hollowness of fruits

A disease that causes the fruit to lack seed material. This is possible when fruit set is disrupted, or due to other factors (temperature changes, lack of pollinators, lack of nutrients, especially potassium, and others). For the purpose of prevention, it is necessary to create favorable conditions for pollination of flowers (humidity, temperature, nutrition, lighting) so that a sufficient number of seeds ripen.

Stolbur

This is a phytoplasmic disease of tomatoes. It is typical for plants in open ground, but in greenhouses it is virtually absent. The main problem is the lack of seeds in infected plants. The main symptoms of stolbur are compacted and brown root bark, compacted fruits, reduced leaves, the plant completely mutates. Stolbur develops in hot and dry weather. The main carriers of the disease are leafhoppers. Almost the only way to deal with stolbur today is to destroy leafhoppers, carriers of the disease.

There is nothing impossible in growing tomatoes; you just need to take preventive actions against diseases and treat diseased plants in a timely manner.

Did you know? Today there are 10,000 types of tomatoes. The largest tomato reaches a weight of almost 1.5 kg, and the smallest has two centimeters in diameter.

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Streak (striking) of tomato is a viral disease that manifests itself in greenhouses or small-sized film shelters.

Its symptoms are very diverse, but its characteristic feature is superficial brownish-red or dark streaks and stripes on the petioles, stalks and stems. Dark spots of irregular shape form on the leaves ( table 14).

Sometimes the disease manifests itself as leaf curl. With severe development of the disease, the affected parts of the plant become fragile, break easily, and the leaves dry out.

If infection occurs early, the plants are so depressed that they almost do not produce a harvest.

Fruits are stunted in growth, angular brown spots appear on them, the fruits often crack, and at the same time, hardening of individual areas of the fruit pulp appears.

Their taste is sharply reduced - they become unfit for consumption. The development of the disease is promoted by low temperature.

The infection persists in the seeds and is spread by pinching, as well as by aphids, mites, and thrips.

Table 14. Tomato diseases:

1 - streak (affected fruits, stems and leaves);
2 - brown spot (affected leaves);
3 - white spot (affected leaf)

Measures to combat streaking of tomatoes

1) collecting seeds only from healthy fruits;
2) dressing the seeds in a 1% solution of potassium permanganate (10 g per 1 liter of water) for 30 minutes, then washing them in warm water and drying them;
3) watering the seedlings with a solution of potassium permanganate (0.5 g per 1 liter of water) 2 - 3 times at intervals of 3 weeks;
4) removal of affected plants;
5) foliar feeding with a weak solution of microelements (solution composition: manganese sulfate - 4 g and copper sulfate - 2 g; boric acid - 2 g and zinc sulfate - 2 g per 10 l of water);
6) spraying with a solution of succinic acid (0.17 g per 10 liters of water): first - after picking, when the plants have taken root; the second - after 10; the third - after 20; fourth - after 30 days;
7) disinfection of greenhouse frames with a 5% solution of potassium permanganate (50 g per 10 l of water) after harvesting;
8) removal of post-harvest plant residues;
9) planting of the variety Gruntovy Gribovsky 1180, which is moderately resistant to viral diseases.

Black bacterial spot

The causative agent of the disease is a bacterium that affects tomatoes from the moment they emerge. The disease is observed both in greenhouses on seedlings and on adult plants in beds.

The disease manifests itself on all aboveground organs of the plant: leaves, petioles, stems and green fruits.

Black spots with a diameter of 0.5 - 2 mm are formed on the leaves, often they are concentrated along the edge of the leaf; on the petioles and stems the spots are elongated, merging with severe damage.

When infected at a young age, plants die.

Green and red fruits are also affected. In this case, small black dots first appear on the fruits, sometimes surrounded by a watery border. Subsequently, the spots grow and reach 5 - 6 mm in diameter. Especially many spots form in the lower part of the fruit, closer to the stalk. On green and ripe fruits, the spots are black, convex, shiny, superficial; on ripe fruits, the tissue under the spots softens slightly. The disease reduces the quality of the fruit and reduces the yield.

Source of infection Seeds and plant residues serve as bacteria on which bacteria can survive for up to 10 years. During the growing season, bacteria are transferred to healthy plants by rain and wind, with splashes of water during irrigation. At the same time, they penetrate into plant tissues through stomata and wounds. The disease develops especially strongly in warm weather with light, frequent rains.

Measures to combat black bacterial spot of tomato

1) crop rotation;
2) disinfection of seeds in a 1% solution of potassium permanganate (1 g per 100 ml of water) for 30 minutes, followed by rinsing with cold water;
3) spraying plants during the growing season, starting from seedling age, with 0.5% Bordeaux mixture (50 g of copper sulfate with the addition of 50 g of lime per 10 l of water), or copper oxychloride, or polycarbacin (40 g per 10 l of water), sprayed 2 times in seedlings and 2 - 3 times in beds;
4) selection of healthy fruits for seeds; 5) collection and destruction of post-harvest plant residues.

Bacterial black spot is a serious disease caused by the gram-negative rod-shaped bacterium Xanthomonas vesicatoria. It mainly affects tomatoes and sweet peppers.

Symptoms of black bacterial spot

Initially, small spots of olive color appear on the leaves, oily in appearance, only about 1-2 mm in diameter. Quite quickly they darken and spread, covering all larger parts of the leaf and stems. All above-ground parts of the plant are affected: leaf petioles, sepals, stalks, tomatoes and peppers. The spots do not merge into large and dark ones, as with late blight, but rather look like a black rash.

The maximum size of one lesion is 5-6 mm, without a light border. As the fruits grow, spots also appear on them, their number increases, by this time the stems and leaves seem to be covered with scabs. Due to malnutrition, the fruits do not ripen, and the leaves gradually dry out and fall off. Yield losses can be 90-100% - rotting of the fruit tissue occurs under the spots. Loss of leaf mass from 50 to 100%.

How does infection occur?

The causative agent of black spot can persist on the seeds of tomatoes and peppers if they have not been disinfected (it is enough to soak the seeds in hot water for 20 minutes at 60°C, or use a disinfectant). Previously, it was believed that the bacterium does not penetrate through the seed coats into the seed but remains on the surface, which is why a great role is given to the prevention of diseases in the pre-sowing period. However, it has already been proven that the pathogen can infect the seed from the inside.

The bacterium penetrates into the leaves during the vegetative development of plants, through stomata, cracks, breaks, any mechanical damage, and spreads to the tissues. The period from infection to the appearance of the first symptoms is approximately 3-5 days, a little longer on fruits.

Conditions under which tomato black spot develops

Favorable conditions for the mass development of the pathogenic bacterium:

• high temperature about 25-30°C, at lower or higher temperatures development is inhibited, but does not stop
• humidity above 70-75% and moisture on the leaves are the best conditions for the development and spread of the pathogen

The acidity of the soil does not matter.

Maliciousness

The bacterial pathogen retains its vital activity as long as there is a food source - the tissue of tomatoes or peppers; they survive on the seeds and green remains of the infected plant. On cleanly harvested soil, the pathogen survives no more than 4-5 weeks. Therefore, in central Russia and Siberia, infection of tomatoes occurs mainly through seed material - the bacteria do not survive the winter, and remain on the seeds for up to one and a half years. But in the southern regions of Russia and the Caucasus, harmful bacteria overwinter in organic residues at above-zero temperatures.

Black spot is most harmful in wet and warm seasons; tomatoes and peppers are especially affected in greenhouses and greenhouses, and in the south of Russia in open ground. After the first plant is infected, in the presence of constant moisture (fog, dew, rainy weather), signs may appear after 3 days; within two weeks, the disease spreads to neighboring plants.

Treatment of bacterial spot of tomatoes

Scientists have identified four different phenotypic groups of the pathogen - bacteria of the genus Xanthamonas, all of them are pathogenic, but different strains have only 70% similar DNA, so breeders have not yet developed varieties resistant to bacterial black spot of tomatoes.

It makes sense to generally select varieties that are resistant to other fungal and bacterial infections.

Prevention is of utmost importance. It is necessary to apply seed treatment in the following ways:

• soak tomato seeds for 10-20 minutes in a 3-5% sodium hypochlorite solution (NaCIO), then wash thoroughly with sterile distilled water
• soak the seeds in a 6-8% solution of calcium hypochlorite (Ca (ClO) 2) for 20-30 minutes, wash thoroughly with sterile distilled water
• treat with trisodium phosphate

The first two products are difficult to obtain and are quite toxic; it is easier to use trisodium phosphate.

Trisodium phosphate seed sterilization method

1. Processing of fresh seeds:

You need to rinse the seeds from the pulp by lightly rubbing them with your fingers.

Wear gloves and sprinkle trisodium phosphate granules over the surface of the seeds (the amount is optional). Stir the wet seeds and lightly rub with the granules until the granules dissolve.

1. Processing of dry purchased seeds:

Dilute trisodium phosphate in water at the rate of 12 g of the drug per 100 g of water. Soak the seeds for 1 hour.

After treatment with trisodium phosphate, rinse the seeds very thoroughly in a sieve; you can leave them under running water for 20-30 minutes.

Treatment of internal seed infection of tomatoes is more difficult, but can be achieved with other treatments. For example, seeds can be soaked in a 1% solution of Planriz (1 ml per 1 liter of water) for 6 hours before sowing. Planriz is a biofugicide, the active substance is the bacterium Pseudomonas fluorescens strain AP-33.

Processing tomato and pepper seedlings

It is worth treating tomato and pepper seedlings 1-2 times with a solution of Planriz or Fitosporin-M. Among other biofungicides, Baktofit and Gamair help cope with bacterial spotting. The drug Fitolavin is very effective on tomatoes - it helps to treat not only bacterial black spot, but also bacterial cancer, tomato blossom end rot and other nightshade diseases.

Fitolavin is sold in ampoules (two pieces, 2 ml each) from the manufacturer “Green Pharmacy Gardener” or in 10 ml bottles from “Green Belt”. Prepare a 0.2% solution (2 ml per 1 liter of water), you can soak the seeds in it before sowing for 2 hours. And after germination, carry out two treatments: the first time with the appearance of 3 leaves, the second - after two weeks. In total, you can spray vegetable seedlings three times. The waiting period for Fitolavin is quite short - about 3 days.

03/14/2013 Plant protection 5657

A.M.Lazarev Ph.D., senior researcher, All-Russian Research Institute of Plant Protection,

F. Popov Ph.D., Leading Researcher, Belarusian Institute of Plant Protection

More than 20 bacterial pathogens infect this crop worldwide. The intensity of their development and harmfulness depends on the soil and climatic conditions of the regions; a third of these bacterial pathogens are still absent in the Russian Federation. The most common and dangerous bacterial diseases in our country are bacterial canker, stem necrosis, bacterial black spot and bacterial spot (mottling).

Bacterial canker of tomato

Bacterial canker of tomato is widespread. This disease is typically vascular in nature. Signs of its manifestation are expressed mainly in the form of withering of plants: bacteria, penetrating the vascular system, cause withering of its shoots. This process begins from the lower tiers of leaves: they experience a loss of turgor (sometimes on one side of the leaf), while the fading parts of the leaf turn yellow along the edge and curl. In some cases, such a manifestation of bacteriosis may be its only external sign.

It can take 1.5-2 months from the beginning of wilting to the complete death of the plant. During primary infection, damage to the vascular ring (in the form of its darkening) is noted in the stems and at the base of the petioles of diseased leaves. Early damage to fruits by the causative agent of the disease leads to their deformity: the seeds darken and lose their viability. Infection of the ground organs of fruit-bearing plants manifests itself in the form of brown sores on young sepals, stems, petioles, especially on the stalks, which causes fruit to fall off. With later infection, the fruits may have an outwardly healthy appearance and normal pulp consistency.

Local manifestation of symptoms of bacteriosis on fruits occasionally occurs in the form of characteristic spotting, which is called “bird's eye”. At the first stage, small affected areas of green fruits look like white spots; at the next stage, when the fruits ripen and color, the center of the spots turns yellow. These birds' eye symptoms can develop on both wilt-affected and non-wilt-affected plants. Sick fruits are delayed in their development and are usually unevenly colored compared to healthy ones.

With severe development of the disease, light brown stripes, cracks and ulcers appear on the petioles and stems, from which yellow mucus protrudes. On a cross-section of such affected organs, the browning of the bundles of the vascular system is clearly visible.

The pathogen enters the plant through mechanically damaged tissue: through injured roots, stems, leaves. At high air humidity, the pathogen is able to infect the plant through open stomata.

Infection of tomato bacterial canker is spread by plant debris, seedlings, and soil, but the dominant role belongs to infected seeds, infected superficially or internally. The pathogen is also transmitted by pinching and pruning plant leaves. With permanent tomato cultivation, the soil serves as a reservoir for bacterial infection. The most favorable conditions for the development of bacteriosis are a temperature of 20...28 o C and a relative air humidity of 80-85%. During the rainy season in hot weather, the spread of the disease can take the form of epiphytotics.

Black bacterial spot of tomato

Black bacterial spot of tomato is quite widespread and harmful, especially in greenhouses. The high harmfulness of the disease is noted in years with hot summers: then the damage to seedlings can be up to 50%, and to fruits - 20%. The harmfulness of bacteriosis manifests itself in damage to the above-ground parts of plants, as a result of which the plant does not produce a fruit crop, or the fruits are of low quality.

Bacteriosis affects the cotyledons, leaves, petioles, stems and fruits of tomato, and young tissues are more susceptible to the pathogen than aging ones. Seedlings and young plants suffer greatly from bacteriosis. At the first stage, very small depressed watery brown spots of irregular shape are noted on the leaf blades of young leaves, translucent in transmitted light and quickly increasing in size (up to 1-2 mm), then the center of the spots gradually turns black. Under favorable conditions for the development of the disease, the spots merge, the leaves curl and dry out. Black elongated spots form on the stems and petioles.

The same picture is observed on the stalks, shoots and pericarps. When the peduncle is severely damaged, massive flower shedding occurs. When fruits are affected in the early phase, dark convex dots, surrounded by a watery border, first appear on their surface, which over time take on the appearance of ulcers. Unlike the typical symptoms of bacterial bird's eye cancer, the dark, scab-like spots are not surrounded by a light border.

The development of black spot is influenced by meteorological conditions. The lower the temperature, the slower the development of black spot. Bacteriosis is transmitted by seeds and plant debris. The infection can persist on seeds for more than a year. Even with a latent infection, seeds can produce apparently healthy seedlings, which in the future can serve as a source of spread of bacteriosis. For this reason, it is important to purchase guaranteed healthy seeds. The pathogen persists for a very long time in parts of plants that are difficult to rot.

Bacterial spotting (mottling) of fruits

Bacterial spotting (mottling) of fruits is somewhat less common than others. Depending on weather conditions, crop losses from bacteriosis in the private sector vary widely (5-30%). The disease is most dangerous during early spring plantings - with high humidity and low night air temperatures.

The disease affects all above-ground organs of the plant (leaves, stems, petioles, flowers and fruits). Small black spots (irregularly rounded) with a yellow edge are usually noted on the leaves; sometimes they are located along the edges of the leaf; the center of such spots is raised, with a yellowish-green halo, then darkens. With the active development of a bacterial infection, these spots merge, causing the leaves to curl and die. Similar spots are noted on petioles, stems and flowers.

Damage to flowers that completely dry out and fall off is especially dangerous. Young green fruits are more susceptible to mottling. At the first stage of the disease, small, slightly convex black spots appear on their surface, surrounded by a whitish (as if watery) border, which then gradually grow (up to 6-8 mm), taking the form of ulcers. Over time, the watery border may disappear. The main source of bacteriosis infection is seeds, but the pathogen is able to survive in the soil and rhizosphere of plants.

Necrosis of the stem core (hollowness)

In recent years, a relatively new bacteriosis for our region, necrosis of the stem core (empty stem), characterized by high harmfulness, has become increasingly dangerous and rapidly spreading. The reduction in yield from premature death of plants can be up to 20-30%. The rapid manifestation of the disease is favored by differences in day and night temperatures, as condensation moisture forms on the plants, as well as the application of excess nitrogen fertilizers.

The initial signs of bacteriosis are observed during fruiting (formation of the second or third cluster): in the central part of the leaf lobes (between the veins) light, rounded-oblong spots appear, which gradually increase in size, and the leaf lobes curl upward (this is especially noticeable on sunny days) .

Manifestations of bacteriosis on leaves, which can be affected in any part of the plant, are very diverse: sometimes necrosis of the apex of the central lobe of leaves is recorded, which spreads like a “tongue” along the central vein. Affected leaves have a “scalded” appearance, although they remain green in color and have dark green oily veins visible. First, small oblong spots are observed on the surface of diseased stems, located mainly 25-30 cm above the soil level. Later, in most cases, necrotic stripes of a dark green color and a length of 25-50 cm develop on diseased stems, which is one of the main characteristics of this disease. In this case, severe maceration of the affected tissues is possible with destruction of the core, from which a mucous white or cream-colored exudate can be easily squeezed out on a cross-section; Bacterial mucilage is sometimes also released from stem scars left by leaves.

At a later stage of development of the disease, cracks with voids inside, with browned core tissue, are often noted in the stems. In the main healthy stems (both in the basal part and along their entire length), a large number of aerial roots are formed, changing color from white to rusty brown, and in the places where they form, the inside of the stem is hollow: it seems that the plant is wasting the contents of the stems for their regrowth. The root system of such plants usually does not show signs of damage.

The process of plant withering develops gradually, and most often their final death is observed during fruiting. In mature fruits taken from diseased plants, double rings may be visible around the peduncle: dark brown in the center and light brown along the periphery. Sometimes short (4-6 mm) rays extend from this outer ring, in the area of ​​which cracks then appear. In some cases, characteristic “networks” of light gray veins are noted on the fruits.

The development of the disease is facilitated by alternating high daytime (above 25 o C) and low temperatures, which leads to the formation of droplet-liquid moisture on the surface of tomato leaves. If conditions for the development of the disease are unfavorable, weakly affected plants (with minor changes in the color of the stem core) may complete the growing season and produce a small harvest of fruit.

The source of primary infection of stem necrosis is seeds and plant debris. A major role in the spread of the pathogen is played by the contact method of transmission of infection during plant care.

Protective measures against tomato bacterioses

Protective measures against tomato bacterioses include a complex of various agrotechnical techniques, as well as the use of biological and chemical means of protection. These measures should be aimed at creating optimal cultivation conditions for plants, which enhances their protective reactions to diseases. On the other hand, the techniques used must simultaneously serve to reduce and suppress bacterial and fungal infections, limit the spread of diseases and create conditions favorable for the development and growth of plants.

Protective measures include:

• the use of varieties characterized by complex resistance to bacterial and fungal pathogens;
• pre-planting seed treatment;
• application of balanced fertilizer rates (excessive unilateral application of nitrogen fertilizers is avoided);
• spraying plants with preparations when the first signs of disease appear;
• careful regulation of temperature and air humidity in the greenhouse (to reduce air humidity, if necessary, the room is regularly ventilated;
• watering strictly between rows - at the root with a small stream (and also avoiding excessive soil moisture);
• regular removal of both heavily affected fruits and diseased plants entirely (along with twine);
• systematic control of weeds and insects (reservoirs of pathogens);
• taking precautions when collecting fruits to avoid mechanical damage;
• collecting and storing seeds from healthy plants;
• thorough cleaning of greenhouses and surrounding areas from debris and plant debris at the end of the season;
• compliance with crop rotation with the return of nightshades to their place no earlier than after 3-4 years;
• carrying out high-quality autumn digging (deeply buried plant residues rot during the winter period).

As a preventive measure, seeds are disinfected immediately before sowing by heat treatment in hot water (48...50°C) for 20 minutes. To warm up, the seeds are placed in a gauze bag and immersed in hot water. The water temperature is maintained within strictly specified limits, since at temperatures above 50 o C the seeds lose their germination, and below 48 o C this method has no effect. After warming up, the seeds are quickly cooled in cold boiled water (3-4 minutes), spread in a thin layer and dried in air (but not in the sun) until they flow.

Positive results against tomato bacteriosis are shown by spraying plants during the growing season with a 0.5% solution of Abiga-Pik, BC (no more than 3 times). Spraying cucumber plants with solutions of other copper-containing fungicide preparations - cuproxate, KS (25-50 g/10 l of water), cartocide, SP (40-60 g), copper oxychloride, SP (40 g), oxychoma, SP (20 g/10 l) – will have a positive effect on reducing the development of bacterial diseases during the growing season. Of the biological products, Fitolavin-300, Baktofit and Gamair show high efficiency. There is information about a significant inhibition of the development of bacterial pathogens by the liquid preparation Planriz, which is living bacterial cells; applied by 2-3 times processing of seedlings and plants.