Black leg potato control measures. How to deal with black leg on potatoes? How to deal with ring rot

based on materials from the St. Petersburg Farmers Assistance Service

Black potato leg

Symptoms of damage: Affected plants are mostly noticeable in early to mid-July due to curling of the upper leaves, yellowing and wilting. With early damage, plants are stunted and then die. Affected shoots can be easily pulled out of the soil. The stem is slightly rotten at the base with varying color from dark brown to black. After a late infection, individual shoots become sick and die. In recent years, other symptoms of damage have been detected in some places: In some plants, the leaves of the leaves wither and die from the bottom up. At first, the stem of the affected shoot feels still strong, but inside it has already decomposed to a slimy state. Nothing is visible externally at the base of the stem.

Defeat conditions: Use of affected planting material, early planting, cold weather at the beginning of the growing season. Cleaning at unfavorable conditions with numerous injuries and damp storage.

Control measures: Cultivation of healthy and flawless planting material, because the pathogen, different kinds bacteria are transmitted only with planting material. Planting too early and deep is not allowed, because the affected mother tuber rots, bacteria enter the stem or penetrate into young tubers. Reducing damage during harvesting and harvesting, and proper storage of potatoes reduces blackleg damage because bacteria can penetrate all damage. Chemical control measures are not possible.

Wet rot of potatoes

Meaning: A very dangerous disease that in a short time during winter storage or transportation forms rotten nests and can destroy an entire batch of potatoes.

Symptoms of damage: The tuber tissue becomes a soft, mushy mass, which is demarcated from healthy tissue by a black line. Without external pressure, the peel does not allow the tuber to fall apart. After cutting, the rotten pulp emits a not very strong basement smell of mold. The colorless pulp darkens when air enters and eventually becomes black -brown.

Defeat conditions: Seed tubers are carriers of bacteria that cause wet rot. When the mother tuber disintegrates, bacteria enter through the lentils, stolons or eyes into the young tubers. Rot does not appear immediately, but only with a lack of oxygen and high humidity during storage; in this case, bacteria are activated. The disease progresses very quickly when the pathogen penetrates the tuber through damage during harvesting and storage. The exposed tissue of unhealed tubers and the presence of moisture on the surface are favorable for the rapid onset of the disease.

Control measures: Minor damage to tubers due to harvesting at soil temperatures above 10 degrees and slow conveyor speed. Drying potatoes immediately after storing them. Tubers should not sweat in the bins. When unloading, it is necessary to take into account the height of the fall. Select rotten tubers in advance. Careful hygiene in the household! Chemical control methods are impossible.

Distribution and harmfulness. Blackleg is widespread in all potato growing areas. In the Russian Federation it is characterized by constantly high harmfulness. The crop shortage can range from 1 - 2 to 50 - 75%. In the Central Black Sea Region, in wet years, crop losses reach 40 - 50%. In the north-west of the Russian Federation - 20 - 30%. In the Primorsky Territory and in the south of the Kamchatka region, 3 - 10 and 15 - 20% of bushes are affected, and in the years of epiphytotics, crop losses in the field amount to 80 and 40 - 50%, respectively.

Characteristics of the pathogen. For a number of years, it was believed that the “black leg” of potatoes is caused by three independent, but closely related species of pectolytic bacteria of the genus Erwinia(syn.: Pectobacterium). Currently, these microorganisms are combined into one species Erwiniacarotovora, which has two varieties - subsp. atroseptica(Esa) and subsp. caratovora(Ess).

Microorganisms E.carotovora - short sticks, straight, with rounded edges, size 0.6 - 1.8 X 1.7 - 5.1 microns, single, connected in pairs or in short chains. They are motile, have peritrichous flagellation, and do not form capsules or spores. Gram-negative, facultative anaerobes. On potato agar, colonies of microorganisms are round in shape, convex-flat, the edge is smooth or slightly wavy, blue, translucent, opalescent in transmitted light, clearly visible after 1-2 days of growth. Bacteria decompose sugars to form acid and gas. Nitrates are reduced, gelatin is liquefied, starch is not hydrolyzed. Milk is curdled, milk is reduced with an indicator. In meat-peptone broth they cause turbidity, and also form a film, ring and sediment.

Symptoms of the disease. The disease manifests itself in the form of wilting and rotting of stems, as well as damage to tubers. With the active development of the disease on the seedlings, yellowing of the lower leaves is observed, the lobules of which curl into a boat and acquire a rigid structure. The upper leaves grow at an acute angle and also turn yellow. Later, the entire bush withers and dries up.

The base of the stem and root system soften and, depending on the varietal characteristics of the plants and weather conditions, take on different colors (brown, dark, yellow, dark green). The affected stems fall under the influence of their own weight and the plant dies. Affected plants, when pulled out of the soil, are torn off at the root collar. With the slow development of the disease, the plant lags behind in growth, the leaves become smaller, but there may be no rotting of the stem. In damp, cool weather, the development of the disease often occurs as rotting of young tissues of the upper parts of the stem in the form of a solid dark green slime (“floating stem”). Symptoms of blackleg on stems are sometimes similar to signs of a fungal disease - rhizoctonia. However, phytopathogenic bacteria cause deep maceration (softening) of tissues, as a result of which the stems easily tear near the surface of the ground when pulled out. In case of fungal infection, the stems remain strong. With rhizoctonia, tuber damage in the form of wet rot is also not observed, except in cases of joint development of two diseases on the plant.

On tubers, the disease usually appears in the field in the second half of the growing season. It is known as wet (soft) rot and is caused by all three species of the genus Pectobacterium. At the site of attachment of the tuber to the stolon, when infection penetrates, a softening of a colorless or light yellow color is noted. Later, a rotted cavity or hollow forms here. Under favorable conditions, decay increases and acquires a specific wine smell. An unpleasant odor occurs later when the putrefactive process includes a large number of saprophytic and semi-saprophytic microorganisms. Signs of disease manifestation vary depending on the species of the pathogen and the varietal characteristics of the potato.

In some cases, the disease manifests itself in the form of softening of those parts of the tuber where the introduction of phytopathogenic bacteria has occurred. Thus, small necrotic spots are sometimes noted on the peel near the eyes. Penetration of microorganisms into plant tissue through mechanical injuries or damage caused by insects, animals and work tools also contributes to infection of tubers. Visually healthy tubers from under diseased bushes, as a rule, contain a hidden (latent) infection.

The transition from the dormant stage to the active stage occurs at the moment when conditions favorable to the pathogen prevail external environment, which simultaneously reduce the mechanisms of host resistance and, at the same time, ensure reproduction and manifestation characteristic features pathogenicity of microorganisms. The disease begins to develop only when the pathogen population in plant tissue, with its continuous reproduction, reaches a critical level - about 107 cells. Average level manifestations of latent infection in offspring from parents who were previously inoculated but devoid of visual signs “ black leg", is 75 - 85% (Powelson M.I., Apple J.D., 1986).

Pathogen specialization. The pathogen is a polyphagous pathogen and affects a large number of both cultivated and wild plant species of different families.

Sources of infection. The main source of infection is considered to be infected seed tubers, where the pathogen can remain latent. In the soil, the pathogen is stored only in unrotted plant residues. Along with the decomposition of diseased tubers and tops, phytopathogenic bacteria also die. However, remaining affected plant debris is a source of infection and recurrence of the disease the following year. This route of infection is more likely in potato monoculture. In addition, the pathogen can be stored in lentils (Nielsen L.W., 1978), in the stolon part of the tuber (Popkova K.V. et al., 1980), in the rhizosphere of various plants and on the surface of stems and tubers overwintered in the soil. of potatoes (Matveeva E.V., 1980).

There are two important ways of spreading bacterial infection: a rotting mother tuber or infected stems and leaves of plants infect healthy daughter tubers in the soil (through soil water), or diseased tubers infect healthy ones through wounds during the operation of harvesting, sorting machines and other mechanisms. The transmission of bacterial infection is influenced by the condition of the tuber skin. In freshly dug tubers, the lentils are open and serve as an entry point for infection. Sick plants can infect injured stems of healthy neighboring bushes by coming into contact with them throughout the growing season.

The disease appears in the first half of summer, 2 weeks before flowering. Sick plants stand out from healthy ones by their depressed appearance and chlorotic coloration of the tops; The leaves of such plants are yellow and curled. Severely affected plants wilt; In clones, individual shoots are often infected.

Most characteristic feature black leg - blackening and rotting of the root collar, as a result of which lateral and additional roots do not develop. Very often, affected plants remain single-stemmed and are easily pulled out of the ground. Since young plants are usually infected, tubers often do not form on them at all; in case of later infection (before flowering), diseased plants produce a harvest, but it is very low. The tubers are small and mostly infected; a small dark spot is visible on the surface of the tubers at the end, from here the darkening spreads inward. The damaged tissue softens and turns into a mucous mass. Cavities with black, uneven, wet edges form inside the tuber. Rot can also develop from the surface of the tuber, which is often observed during potato storage.

The causative agent of blackleg is the bacterium Erwinia phytophthora Berg. IN winter period the bacteria persist in infected tubers. In unrotted remains (stems), bacteria can overwinter, but directly in the soil they quickly die. Therefore, the main source of the disease is planting material.

When planting infected tubers, bacteria enter the soil. They penetrate the underground parts of the plant through various damage - mechanical, damage by soil insects, nematodes. But most often, bacteria penetrate the stem from an infected mother tuber. If bacteria are introduced with infected tubers into storage or piles during the winter period, mass rotting of potatoes is possible.

The development of blackleg depends largely on soil and meteorological conditions. Blackleg is especially noticeable on clayey, moist soils; humid and moderately warm weather also favors the development of the disease.

Blackleg is widespread, especially in the non-chernozem zone, in the BSSR, in Western and Eastern Siberia and in other areas.

Control measures

1. Selection of healthy planting material; disinfection of tubers before vernalization (see black scab).

2. Cleaning potato plantings three times, i.e. removing diseased plants. The first cleaning is carried out in the spring after seedlings, the second - during flowering and the third - before harvesting. This activity is necessary in seed plots to obtain healthy planting material.

3. Drying of tubers in the field and, if necessary, additional drying before storing them. Especially great importance drying and light-hardening are used for seed potatoes.

4. Compliance with the rules for storing potatoes (see late blight).

5. Use of resistant varieties. Relatively stable: Pirmunes, Viliya, Detskoselsky, Skorospelka 1, Kameraz 1, Slev, Ulyanovsky, Agronomichesky, Veselovsky 2-4, Karnea, Borodyansky.

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Potato blackleg is a bacterial disease. It starts from the roots of the potato and gradually covers the lower part of its stems. Blackleg spreads most when growing potatoes in damp and cold soil, during prolonged rainy and cool weather.

Signs of root crop damage by black leg are wilting of young potato tops, as well as curling and yellowing of its leaves. Potato bushes affected by black leg are easily pulled out of the ground; the stems of these bushes are black and rotten.
Blackleg is transmitted to tubers, which are often infected with this disease in the fall during potato harvesting when they come into contact with already infected tops.

Measures to combat potato blackleg

The main measures to combat potato blackleg are removing diseased plants from the area and dusting the place where they grew with a mixture of copper sulfate and wood ash. It is prepared by adding a tablespoon of vitriol to a glass of ash.

Another measure to combat blackleg is to spray the plants before their first hilling with a solution of the Energen preparation. It is made by adding 10 milliliters of energy to 10 liters of water.

Potato plants with black leg and their tops must be burned after harvesting, and the dug up tubers are thoroughly dried and sorted before storing.

Black leg on potatoes is often a sign of disease. You can easily distinguish traces of overwatering from plant disease simply by looking closely at it.

If the stem falls off on its own or the plant is easily pulled out, and there are no visible signs of moisture, then most likely there is an infection with black stem.

Primary diagnosis can be carried out very in a simple way: Take the darkened stem of the plant and dip it in water, it will become cloudy. Such a simple check can help determine the cause of plant damage.

Previously, it was believed that blackleg disease was caused by three types of bacteria. Currently, they are all combined into one species called Erwinia carotovora. This type has two varieties: subsp.atroseptica (Eca) and subsp.ceretovora (Ecc).

Under a microscope you can see the microorganisms E. Carotovora. The bacterium has short rods, straight, with rounded edges. The average size equals 0.6 - 1.8 x 1.7 - 5.1 microns. They can be single, connected in pairs or in short chains. The bacterium is characterized by mobility and does not form capsules or spores. They are classified as gram-negative, facultative anaerobes.

Diagnosis and prevention of the disease can be done at the stage of planting the crop. To do this, let's move on to the symptoms and causative agents of the disease.

Symptoms and causative agent of the disease

The disease does not always manifest itself immediately. Most often, its signs are visible in the first half of summer, usually two weeks before flowering.

Affected plants look much worse than their healthy counterparts: they look depressed, the color of the foliage changes, the leaves may be stunted yellow and curled.

Individual shoots in a bush may be infected, but the entire course may wither at once.

A clear sign of the disease is rotting of the plant roots and blackening of the stem. Due to this, additional roots stop developing.

If you try to pull an infected plant out of the ground, even a child can easily do it, since it is extremely easy to pull out a plant.

As a rule, infected plants do not develop and remain single-stemmed and do not form tubers.

If infected at later stages (before flowering), the plant produces a harvest, but it will be minimal.

Externally, you can examine the tubers and notice small dark spots, this darkening spreads inward. The affected fruit darkens and turns into an unpleasant slimy mass. Rot is present on outside tuber and inside the fruit. Externally - rot and a slimy mass, inside - weeping black and jagged edges.

Diagnosis of infection

Having examined the stolon part, you can even notice changes with the naked eye. The bacteria spread, moving from the stems to the daughter tubers and, spreading to the middle, transform the stolon into a rotting soft mass with an unpleasant odor. The color of these parts of the tuber also changes: from light it becomes quite dark.

Another feature of affected tubers is an unpleasant-smelling liquid flowing from cracks. Cavities form inside the tuber, and cracks and dark skin appear externally.

In dry conditions, infection occurs in a chronic form.

Diseased plants are detected after germination. The leaves immediately lose melatonin, turn yellow, curl up and dry out; the stem turns yellow and withers.

Rapid development of the disease. Period - from 4 to 6 days. Environment - high humidity, hot weather. Plant changes: the stem breaks under its own weight. The leg turns black and rots.

The difference from Rhizoctonia is that plants are easily pulled out of the soil. Additionally, on transverse sections there is browning of the vascular bundles.

Causes of infection

Biology of blackleg

Blackleg affects not only potatoes. It can also occur in other cultures. Lettuce, cabbage, radishes and garden crops are at risk. The signs of infection in these plants are exactly the same: the stem rots, the plant withers and the leaves change color.

The reason is all in the same Carotovora bacteria. Sources of infection: soil, planting material, vectors of infection.

Sick plants can tolerate diseases in different ways: from developmental delays to complete wilting.

Fighting methods

Preventive measures against blackleg. Biological agents

Preventive measures to protect against Blackleg. Chemicals

• Before planting, tubers are sprayed with TMTD or Fitosporin-M preparations.

• The earth can be watered not only with a solution of manganese, but also with chemicals that are applicable to combat fusarium. For example: foundationazol, vitaros, topsin-M, bental or previkur in the proportion of 2 grams of the drug per 1 liter of water.
• For prevention, watering with the addition of “Effecton” is used in the proportion of 3 tablespoons per 10 liters of water. Consumption per plant is half a liter of water. The solution must be heated to twenty-five degrees.
• Before storing potatoes, they are treated with the drug “Maxim”.

Review

Anastasia

We decided to grow potatoes where they grew last year. We thought it was all nonsense and there would be no problems. This was not the case: even as the potatoes were sprouting, they began to turn into something unknown. It was getting blacker and darker, we already thought we couldn’t save it, but a neighbor suggested good drug Energen, we treated it and everything seemed to go away.