Diseases of white cabbage seedlings: downy mildew. Downy mildew of cabbage. Bacterial and viral diseases of cabbage: symptoms and control methods

Let's consider cabbage diseases such as downy mildew or false powdery mildew and mosaic - viral infection cruciferous

Cabbage diseases. Downy mildew

Downy mildew (downy mildew) . The causative agent of downy mildew, or downy mildew, is a fungus that spreads especially widely on cabbage heads during storage in a humid environment. Downy mildew affects both seedlings and seed cabbage.

With this disease, the cotyledons become covered with yellow spots, then the yellowness spreads to the leaf blades. The bottom of the leaves are covered with a white coating - these are spores of a multiplying fungus. Affected leaves dry out and fall off. IN open ground The seedlings initially grow normally, but then reddish spots appear on the upper part of the leaf blades, and white coating.

In the storage room, heads of cabbage infected with downy mildew disappear completely.

The seed plants in the field become covered with dark spots; shiny, almost black formations appear on the leaves, stems, peduncles and seeds. After prolonged rains, a white coating forms on the spots. The seeds remain underdeveloped. They become a source of further infection of cabbage, as well as radishes, turnips, rutabaga and radishes.
The infection persists in plant debris if it is not destroyed in time in the beds. To a greater extentDowny mildew persists in some of the mother cabbage plants for a long time, both in open ground and in storage.

Control measures : To prevent the occurrence of this infection, cabbage varieties that are resistant to downy mildew should be selected. However, they are not absolutely resistant to the fungal disease downy mildew. Therefore, you should not forget to spray the plants with 1% Bordeaux mixture with adhesives.
In greenhouses, it is necessary to ventilate plantings of cruciferous crops more often.

Cabbage diseases. Mosaic

Mosaic is a viral infection that appears about a month after cabbage is planted in the ground, when with the naked eye you can already see how the veins on young leaves turn yellow. Mosaic virus most often affects cauliflower, but can also occur on other types of vegetable crops, even wild ones, from the cruciferous family.

The lower leaves are affected by the mosaic much later: dark green stripes appear on their large veins. The veins stop growing, so the leaf blades appear wrinkled. The growth of cabbage slows down very sharply, and flowers do not appear on the seeds.

For mosaic-affected cabbage, the most dangerous time in the summer comes when the air temperature is within room temperature - 16–18 ° C. The onset of heat can smooth out the symptoms of mosaic, but with a new drop in temperature, the infection seems to return to the cabbage again, with all the ensuing consequences.
Characteristic signs of the disease may appear on only one half of each leaf blade, but the plant suffers no less from this.
Note: The mosaic virus, as a rule, causes irreparable damage to the plant, so throughout summer period You need to regularly inspect the leaves of cabbage and other cruciferous vegetables so as not to miss the onset of the development of a viral disease.

Control measures : To prevent the virus from being carried inside the leaf tissues, leaf-eating pests should not be allowed to multiply in the cabbage bed. Weeds from the cruciferous family must be removed not only between the rows, but also outside the garden.

Before planting in the garden, you should carefully inspect top part plant leaves. Seedlings with signs of mosaic need to be rejected and destroyed immediately. It is not recommended to plant cabbage in the same place where a mosaic infection was found in previous years.

Material prepared by: agronomist O.I. Buynovsky

Downy mildew

Peronosporosis, or downy mildew. The causative agent of the disease is the fungus Peronospora brassicae Gaum.

It affects cabbage, radishes, rutabaga, turnips, turnips, watercress and some weeds, especially shepherd's purse, at any age, but is most dangerous for young plants.

The mycelium of the pathogen develops in the intercellular spaces of tissues. Forked-branched conidiophores protrude to the surface, on which conidia are formed. The fungus overwinters in the form of oospores on fallen leaves. Optimal conditions for the causative agent of the disease they are formed at a temperature of 8-12°, for the development of the disease - at 10-15°.

Downy mildew manifests itself on cotyledons and true leaves in the form of gray-yellow blurry spots. On the underside of the leaf a weak, loose, light gray or almost white coating is visible, consisting of conidiophores and conidia.

Under conditions favorable for the development of the disease, the spots enlarge and cover the entire leaf blade. Severely affected leaves die prematurely, which can lead to complete death of the seedlings. Distinctive feature The manifestation of peronosporosis on radishes is that sometimes root crops are affected, which crack and become covered with dark spots.

In the testes, all above-ground organs are infected: leaves, stems and pods. Affected young shoots become deformed and dry out without setting pods. On pods and stems, the disease manifests itself in the form of dark elongated spots covered with a sparse white coating of the fungus.

The main source of infection for the first-year crop is seeds and post-harvest plant residues; for the second-year crop, it is queen cells and cabbage nurseries located near the seed areas.

Lodging of plants, inclination of the stem (stem P.) or the entire plant (root P.). Stem rot is caused by a large mechanical load of the above-ground mass on the lower part of the stem. It is observed with heavily thickened crops, increased nitrogen nutrition, abundant watering, shading, with the development of climbing weeds in crops, fungal diseases of shoots and roots.

cabbage protection pest

Characteristics of cabbage diseases

Table 2. Characteristics of cabbage diseases.

Name of diseases	External functions of disease manifestation	Place and form of persistence of 1 infection	Stage 2 infection	Conditions favorable for the occurrence of disease conditions.
Xanthomonas campestris pv. campestris (Pammel) Dowson - Vascular bacteriosis of cabbage.	Dark-colored vessels of leaves, petioles and stumps	on seeds and plant residues		temperature 20-240 C and air humidity 80-100%
Mucous bacteriosis, caused by Erwinia carotovora Holl. (jon.), Erwinia aroideae (Town) Holl., Pseudomonas Sp	Oily spots form on the leaves of seedlings, which, increasing in size, merge	on seeds, seedlings and heads of cabbage		warm and humid weather, especially on weakened or pest-damaged plants.
Downy mildew. The causative agent of the disease is the fungus Peronospora brassicae Gaum.	Gray spots appear on the underside of the leaves, and brown spots appear on the stems, leaves and pods themselves	seeds, post-harvest plant residues	queen cells and cabbage nurseries located near seed plots	The disease develops at high air humidity. temperature 8-12°

Conclusion: one of the reasons for the low cabbage yield in the country is high crop losses from diseases. Mucous bacteriosis forms rot with a characteristic unpleasant odor, gradually they are completely covered with mucus and rot. Soon the process of rotting begins inside the head of cabbage and stalk. Young plants affected by vascular bacteriosis die prematurely. Older plants develop unevenly. Downy mildew (peronosporosis) is a very dangerous disease for cabbage. It causes yellow blurry spots to appear on the cotyledons and leaves of seedlings, the leaves turn yellow and die, and the plants stop growing. Therefore, it is necessary to choose the optimal timing of the first and subsequent treatment with fungicides.

All garden crops, including cabbage, are susceptible to diseases. It is much easier to take preventive measures against infection with them than to treat acquired ones. Moreover, some of them cannot be treated.

Bacterial and viral diseases of cabbage: symptoms and control methods

The entire edible part of cabbage is above the ground, so treating it with pesticides to kill cabbage diseases means harming your own health. Toxic substances that pose a danger to the human body, when absorbed into the leaves, accumulate there and remain forever. Therefore, prevention, especially traditional methods, is always preferable.

A disease of cabbage called mucous bacteriosis occurs mainly during storage, when the temperature is significantly increased. The disease develops due to bacteria and occurs in two ways: the outer leaves rot, an unpleasant odor emanates from them, then the stalk begins to rot; the second option is that rotting begins from the head of cabbage, mucus forms, and then the leaves are affected. The possibility of disease is facilitated by too large doses of nitrogen, heavy rainfall or watering, and failure to observe crop rotation. For prevention and control you should:

grow hybrid varieties that are immune to the disease,
destroy pests throughout the season,
do not disturb crop rotation,
carry out disinfection in places where crops are stored,
observe the storage temperature conditions,
treat the seeds before planting,
treat the roots of seedlings (“Fitoflavin-300”).

Vascular bacteriosis in cabbage occurs at any stage of development: the disease enters the plant with insects or during rains. It manifests itself as yellowing of the affected leaf, then the veins on it turn black. Subsequently, the leaves darken completely and die. The problem is that the bacterium remains viable in the soil for up to two years. Control and prevention measures:

Plant hybrids, they are more stable;
Plant in the same place after at least four years;
Remove weeds in a timely manner.

You can treat with a 0.1% Binoram solution, spray the seedlings with 0.2% Fitoflavin-300, and the roots of the seedlings can be dipped in the same solution. Before planting, treat the seeds with garlic infusion.

This viral disease is spread by cruciferous weeds infected with aphids. At first, the veins of the cabbage lighten, then they stop growing, and the leaf wrinkles. Prevention is the fight against aphids and weed removal; the disease cannot be treated. Affected heads of cabbage should be dug up and burned.

Fungal diseases of cabbage: symptoms and methods of control

Almost all fungi are grown in a humid environment, due to improper storage or neglect to disinfect seeds or seedlings.

Alternaria (black spot)

Most often, the disease appears in places where seedlings are stored and harvested. Black stripes and spots appear on the seedlings, which causes wilting. In adult plants, the spots are accompanied by a coating of soot. Sometimes plaque gets inside the head of cabbage, which is also accompanied by spots that spread to the leaves. Preventive actions: hydrothermal treatment of seeds or their treatment with TMTD, compliance with crop rotation and timely removal of weeds. During the growing season, it can be treated with preparations containing copper.

This disease develops in damp and cool weather, during the period of head formation. The main signs of the disease appear already in the storage facility. Mucus appears on the leaves, and black dots of spores of this fungus grow around the lesion.

Prevention consists of disinfecting the storage; harvesting should only be done in dry weather, leaving three centimeters of the head of cabbage in the ground and a couple of lower leaves. If an infection is detected in a storage area, the affected areas are removed and covered with chalk.

White rust

Kila

The causative agent of clubroot in cabbage is cystospores of a lower fungus stored in the soil. The insidiousness of the disease is that at an early stage it is difficult to notice. It can only be detected by digging up the cabbage; there will be growths of different sizes on its roots. A sign of the disease is wilting of the leaves. The disease spreads in damp, cool weather, with affected seedlings. Therefore, before planting, inspect the seedlings. Treating the soil with slaked lime will help prevent clubroot infestation; you can also use fungicides.

Important! Under no circumstances should clubroot-affected leaves be fed to livestock. The fungus will go into the manure, further in a circle.

Downy mildew (peronospora)

Downy mildew infection occurs through seeds or soil. Both seedling shoots and adult cabbage are sick. The first signs of the disease appear on young leaves in the form of yellow spots on the outside of the leaf. As the disease spreads, a gray putrid coating called spores appears on the leaves.

For prevention, treat the seeds before sowing and maintain crop rotation. If a disease appears, treat the cabbage with Phytophthorin - this is a biological product.

Powdery mildew

Foci of powdery mildew are covered with a white coating in the form of powdery powder. Since plaque is wiped off like dust, many people perceive it that way. There is a gray coating on the inside of the leaf, and yellow spots appear on the outside. As soon as you notice this, start treating with Fitosporin-M, apply once every three weeks until the disease is completely eliminated.

Damage occurs when soil gets on the leaves. First, orange-yellow spots appear, which gradually spread the infection to the entire plant, ulcers form on the leaf petioles, the root collars turn yellow, the roots become worn out, and the plant dies. When a disease appears, spray the plant with a 0.2% solution of copper oxychloride. Preventive measures consist of observing the conditions for planting and development of cabbage.

Gray rot

With this disease, damage occurs in the place where cabbage is stored. Fungal spores develop well in high humidity, inhabiting cabbage heads with fluffy mold, while cabbage leaves are covered in black spots. Preventive measures:

During the growth period, monitor watering; it should be moderate;
Do not overdo it with nitrogen fertilizing;
Remove dry and yellowed leaves from the head of cabbage;
Disinfect before storing crops.

Dry rot (fomoz)

Cabbage blight appears as white spots with dark spots on cabbage leaves. It can be confused with blackleg, but with this disease the diseased areas are gray, and the underside of the leaf is lilac. Methods of spraying “Fitosporin-M” on affected areas help here, and for prevention, before sowing, treat the seeds with Tigam 0.5%.

Cabbage blackleg is a rather dangerous infection; it is important to figure out how to fight this fungus, because it multiplies very quickly. The causative agent of the disease is in the soil and feels good when elevated level acidity and humidity. Cabbage, planted too often and overfed, is most susceptible. nitrogen fertilizers. Sick plants dry out, the root collar becomes thinner, and the lower part of the trunk of seedlings affected by the fungus rots.

Before planting, it is necessary to disinfect the soil with a 1% solution of potassium permanganate and treat the seeds with Fundazol or Planriz. Unfortunately, there is no treatment: diseased plants are removed, burned, and the soil is disinfected with potassium permanganate.

When affected by late blight, the fungus spreads from the stem to the leaves, affecting the head of cabbage. The shoots covering the head of cabbage become dark brown in color. White spore fluff is visible between the affected leaves. Yield loss due to late blight - 50% of fruits.

Did you know? The disease was discovered in 1974 in storage facilities in England, in 1984 it affected cabbage in Germany, and in 1996 an outbreak of late blight was diagnosed in Russian storage facilities.

It is not yet known how to process cabbage in this case. There are only preventive measures: compliance with crop rotation, disinfection of soil and seedlings, and also do not plant bulbous plants nearby

Attention! Harvesting immediately after rain, without allowing the cabbage to dry out, will significantly increase the possibility of late blight infection.

Fusarium wilt (tracheomycosis)

The popular name is jaundice, since with this disease the leaves turn yellow and do not set into heads. Even if it closes, it will be a wrinkled, lopsided plant with fallen lower leaves. This infection can destroy most of the crop. There are no methods to combat this cabbage disease. For prevention, diseased plants are removed and the soil is treated with solutions of manganese and potassium or copper sulfate.

Summary:

In young plants, on the cotyledons and leaves, on the underside, a grayish coating forms in the form of single or merging spots, which represent conidial sporulation of the fungus. Vague spots of pale yellow color appear on the upper side of the leaves. Affected leaves turn yellow and gradually die. In testes, the fungus damages all parts of the plant (stems, leaves, pedicels, pods). A white powdery coating forms on them, and the tissues in the affected areas darken and are depressed. Affected seeds become dull, puny and form affected seedlings during sowing, since the fungus begins its development simultaneously with the plant, penetrating its tissues. The mycelium of the fungus grows between the cells of the plant tissue, after which dichotomously branched conidiophores protrude to the surface through the stomata. They produce single-celled conidia 12-28 x 11-23 µm, elliptical, with a colorless, thin shell. The main source of infection is infected mother plants, on which the pathogen can be in a dormant stage, in the form of oospores. In addition, the fungus and its spores are well preserved on plant debris and in seed coats. For example, fungal mycelium can remain viable in cabbage seeds for 6 years or more. Disease ( Downy mildew of cabbage or cabbage downy mildew (Peronospora brassicae Gaum.), in addition to cabbage, affects rutabaga, radishes, turnips, as well as other plants, belonging to the Cruciferous family. The disease occurs in North America, Western Europe and almost throughout the CIS. Seeds, plants and testes are especially strongly affected in the Volga-Vyatka and Central regions, the North-Western zone, Lipetsk, Tambov, Voronezh regions, in Ukraine, in Krasnodar region, CCR, Uzbekistan, Eastern Georgia. Seed damage, especially in the southern regions, is facilitated by heavy rainfall during seed formation (75-80 mm), high humidity (more than 75%), daylight hours of 14-15 hours, and optimal average daily temperature (19-23°C). Similar factors contribute to the spread of the disease in the northern regions. In some years, the percentage of infected seeds can reach 50-60%, which leads to a reduction in yield by 16-20%. Losses on queen cells are 30-60 c/ha. From 30 to 100% of seedlings can die from peronosporosis. The percentage of infected testes can reach 32-100%. To prevent the development of the disease, it is necessary to collect seeds only from healthy plants, disinfect seeds and greenhouses before sowing, treat seedlings with chemicals, remove plant debris, discard infected seeds before planting in the ground, and select varieties resistant to the disease.

Measures to protect against peronosporosis (downy mildew) of cabbage:

white cabbage

They observe fruit rotation and return the cabbage to its original place no earlier than after 3 years.

cold water

When growing seedlings, do not allow excessive air humidification.

When signs of peronosporosis appear on the seedlings, spray with a 1% solution of Bordeaux mixture or with preparations such as Ridomil Gold MC, Acrobat MC.

We discuss topics: cabbage diseases, plant diseases, peronosporosis, downy mildew

Downy mildew of cabbage ,
cabbage downy mildew

Pathogen- Peronospora parasitica Tul.
Systematic position: Group Protista Haeckel, department Oomycota Arx, class Oomycetes (Oomycetes G. Winter), order Peronosporales E. Fisch., family Peronosporaceae.
Morphology and biology. The fungus, located in the intercellular spaces of plant tissues, forms conidial sporulation that reaches the surface through stomata. Conidiophores are 1-2, 250-450 x 6-9 µm in size, dichotomously branched. Conidia are unicellular, elliptical, 12-28 x 11-23 µm, with a thin, colorless shell. Often spherical oospores, 25-30 microns in diameter, are formed in plant tissues. Conidia and oospores germinate as a mycelial sprout. The main source of infection is infected plant mother liquors, in which the fungus is found in the form of oospores. The causative agent of the disease also persists in the seed coat and on plant debris. The fungal mycelium in cabbage seeds remains viable for up to 6 years. Ecology. In the southern regions of seed production, seed damage is favored by heavy rainfall (75-80 mm during the period of seed formation), an average daily temperature of +19...+23 o C and a relative air humidity of more than 75%, as well as a day length of 14-15 hours; V northern regions- heavy precipitation, average daily temperature +10...+15 o C and relative air humidity 80-90% and the same length of daylight hours (14-15 hours). Spreading. The disease has been reported in Western Europe and North America. In the former USSR, downy mildew is registered everywhere. Severe damage to plants, testes and seeds is observed throughout the North-Western zone, as well as in the Central and Volga-Vyatka regions and some regions of the Black Earth Region (Tambov, Lipetsk and Voronezh), in the Krasnodar Territory, in the Crimea, in Ukraine (Kharkov region. ), Uzbekistan (Tashkent region) and in Eastern Georgia. Damage. The disease manifests itself on plants during all periods of their development, but seedlings and seeds are especially severely affected. On the cotyledons and leaves of seedlings, a grayish powdery coating of conidial sporulation of the fungus appears in the form of separate or merging spots on the underside of the leaf. On the upper side of the leaves there are pale yellow blurry spots. Diseased leaves turn yellow and die when severely damaged. On the testes, leaves, stems, pedicels and pods are affected, on which a white powdery coating forms, under which the tissue is pressed in and darkens. Seeds in affected pods become dull and puny. When sown, such seeds produce diseased seedlings with diffuse development of mycelium in them. Economic importance. The fungus attacks cabbage, rutabaga, turnips, radishes and other cruciferous plants. In years favorable for the development of the disease, seed contamination reaches 50-60%, due to which the yield is reduced by 16-20%, and on mother plants the shortage of cabbage is 30-60 c/ha. Damage to seedlings by peronosporosis is observed from 30 to 100%. Infection of testes in some farms reached 32-100%. During storage of cabbage, the disease can develop on the outer leaves of the cabbage heads and cause rot of the stumps. Control measures. Collecting seeds from healthy testes and disinfecting them before sowing; disinfection of greenhouses; treatment of seedlings in greenhouses and in the field with chemicals; normal sowing density and ventilation of greenhouses; destruction of all post-harvest residues; thorough inspection of the seeds before planting in the field; crop rotation; growing resistant varieties.
Sources of information:
Bilay V.I., Gvozdyak R.I., Skripal I.G. "Microorganisms - pathogens of plant diseases." "Naukova Dumka", Kyiv, 1988
Ed. Peresypkina V.F. "Diseases of agricultural crops." "Harvest", Kyiv, 1989