How to deal with potato ring rot. Potato diseases, their treatment and prevention

Distribution and harmfulness. Ring rot is widespread in the Russian Federation and the CIS countries, in many countries of Europe and America. According to the European and Mediterranean Plant Protection Organization (EPPO), this disease is most widespread and harmful in the USA, Canada and Russia.

In Russia, ring rot is found everywhere both in the European territory and in the Urals, Siberia and the Far East. In the CIS countries, this bacteriosis is common in Belarus, Ukraine, Kazakhstan and the Baltic states.

The disease is among the harmful ones, yield losses range from 11 to 44.5%, and increase significantly during storage. Some authors believe that losses can reach 60 - 70%. In a number of countries, certification of seed potatoes has been introduced, which involves the rejection of the entire batch, if among the 400 tested tubers there is at least one affected by ring rot.

Characteristics of the pathogen. The causative agent of ring rot is bacteria of the species Clavibactermichiganensis subsp. sepedonicum(Cms) (syn.: Corynebacteriumsepedonicum).

Baktersh are short sticks (straight or slightly curved) with rounded edges, 0.3 - 0.6 x 0.8 - 1.4 microns in size, single or connected in short chains or in pairs. They do not have flagella, they stain positively according to Gram, aerobes

Disease symptoms. The disease affects leaves, stems, stolons and tubers. When heavily infected tubers are planted, some of them rot, and plants grow from the rest, on which the first signs appear on the leaves in the early stages. The surface between the veins of each leaf takes on a pale yellow color, giving the leaves a speckled appearance. The upper leaves gradually turn yellow, some of them curl in one direction. The lower leaves become thin and sluggish, their edges can twist upwards. There is a shortening of internodes, which causes dwarfism of plants and a close arrangement of stems.

When planting weakly infected tubers, the first symptoms of damage appear during flowering in the form of withering of one or two stems in the bush. Later, brown spots appear at the ends of the lobes of withered leaves. Withered stems, unlike other diseases (fusarium, verticillium), fall to the ground. Slow wilting of the bush may last until harvest. In some cases, a white, creamy or yellowish slimy mass is released on the underground part of the stems, which serves as a diagnostic sign for potato ring rot.

The described forms of manifestation of bacteriosis are the result of the penetration of the pathogen along the stolons from the infected seed tuber into the stems. Bacteria gradually accumulate in the vessels and cause blockage. The leaves lose turgor, the plant wilts (wilt). A number of researchers also associate the wilting of potato plants with the release of a phytotoxic polysaccharide by bacteria (Spensor and Gorki, 1961). On tubers, ring rot manifests itself in the form of damage to the vascular ring and pit rot (yellow subcutaneous spotting). The causative agent of the disease penetrates into young tubers at the early stages of tuberization through stolons. The vascular system of the tuber softens and acquires a light yellow color. When pressed, a light yellow mass is released from the affected vessels. The lesion often starts from the stolon end of the tuber, however, foci of decay can also be in other places in the vascular system. Later, the disease covers nearby tissues and the core of the tuber. In some varieties, the rotting zone in the form of a cone extends from the stolon part to the core. Ultimately, wet rot develops when the tissues are completely destroyed and turn into a white, viscous, unpleasantly smelling mass. Affected tubers sometimes develop pink or light brown surface spots and cracking near the stolon and lentils.

The pitted form of ring rot occurs when bacteria penetrate through skin wounds in the autumn, but in the early stages there are no external symptoms of the disease. The disease manifests itself and can be detected after 5-6 months (at the end of winter-beginning of spring) in the form of the formation of round spots of cream or light yellow color under the skin. At first, they are small in size (2-3 mm), but gradually expand and deepen, reaching a diameter of 1-1.5 cm. Eventually, pits are formed that reach the vascular ring, causing it to become infected.

Bacterial ring rot is often confused with tuber lesions caused by genus fungi. Fusarium,Verticillium, bacteria Ralstoniasolanacearum. The main diagnostic sign indicating WITH.michiganensis as the causative agent of the disease, in such cases, yellowing of the vascular ring and the formation of a light yellow mucous mass protruding from the vessels when they are squeezed are considered. In contrast, the causative agent of brown rot R.solanacearum causes browning of the vascular ring of the tuber.

Many researchers have noted that when planting outwardly healthy tubers, diseased plants grow. The pathogen can be transmitted to offspring for several generations without visible symptoms. In the years of development favorable for him, an outbreak of the disease is observed on such material.

pathogen specialization. Potatoes are considered the only natural host with. michiganensis. In experiments on artificial inoculation of plant species botanically close to potatoes, the susceptibility of a number of species has been shown, and some of them (tomato and eggplant) are used as diagnostic indicator hosts (Langerfeld E., Rohloff H., 1988).

sources of infection. Affected tubers are the main source of infection persistence and its transmission to new crop tubers. It is believed that bacteria do not persist in the soil, unlike the causative agent of brown rot. However, there is evidence that the causative agent of ring rot can persist for a long time in unheated rooms on any surface (Nelson, 1978).

Healthy tubers can become infected by contact with rotting ones, especially if they have scratches, areas with peeled skin-swarm. In this case, tissue damage is observed in places where bacteria enter - pitted rot. The cutting of potatoes especially enhances the re-exposure.

Ring rot is a bacterial disease of potatoes that affects the conductive vessels. It can be found in any area where potatoes are cultivated. Losses from the disease can reach from 10 to 40%. The causative agent is the bacterium Corynebacterium sepedonicum. Refers to quarantine diseases of potatoes. High temperature and humidity contribute to its spread.

Infection of tubers occurs during the harvesting period, with mechanical damage to the tubers. Non-observance of technology when cutting tubers before planting. It affects tubers (causes rotting) and tops (complete wilt).

The characteristic signs of this potato disease appear on the plant in the flowering phase. Single stems begin to turn yellow and wither, the bush falls apart. With severe damage, the plant dies. Planting contaminated materials leads to mixed results. Some of the tubers rot in the soil, the rest germinate, but it will not work to get a crop from them. A severe infection of the planting tuber causes shortening of the internodes (dwarfing), the upper leaves gradually turn yellow and curl, the lower ones are thin, sluggish and curled up. The stems in such bushes are located very close to each other. Weak infection of planting material appears only in the flowering phase (withering of several stems in one plant). After that, brown spots appear on the withering leaves. This process can continue until cleaning.

A distinctive feature of this potato disease is the discharge of creamy or yellowish mucus on the underground part of the stem.

In cold and wet years, the disease proceeds in a latent form. On tubers, the disease manifests itself in the form of a vascular ring and subcutaneous spotting. When the infection enters through the stolons, the vessels of the tuber become soft and, when pressed, a yellow substance is released. Outwardly, such tubers are no different from the general mass, but after a short period of storage, the tubers completely rot and turn into a disgustingly smelling mass. When the infection penetrates through mechanical damage during harvesting, the disease manifests itself only in the spring. Under the skin, in the affected areas, spots of light color are formed. The pulp here decomposes and a hole forms (pitted rot or yellow subcutaneous spotting). When planted, infected plants grow from such tubers. Elevated temperature during storage causes the rapid development of ring rot. Pit rot can be attributed to the primary source of infection of a further crop.

Ring rot develops very slowly; by the end of flowering, bacteria begin to move from the tubers to the stems. In the process, there is a blockage of blood vessels, the water supply stops, the leaves turn yellow and wither, the process of photosynthesis stops, the stems fall to the ground.

Pit rot (the primary form of a bacterial potato disease) - infection occurs in autumn during harvest. Bacteria penetrate initially into the tuber, then in the spring after planting, into the green parts of the plant.

From the latter to young tubers (ring rot). High humidity and temperature (20-25°C), optimal conditions for the development of the disease. Bacteria also release toxic toxic substances. The pathogen overwinters in tubers and on plant debris. All measures to combat ring rot are aimed at preventing infection of planting material with the disease. First of all, you need:

• For planting, use only healthy material.
• Use varieties resistant to this potato disease.
• Timely removal of tops and plant residues.
• Drying potatoes before storage.
• Preparation of storage facilities for potatoes.
• Germination of seed material in the light. Allows you to identify infected tubers.
• Removal of diseased plants from the field.

Compliance with such elementary rules will allow you to avoid trouble with this bacterial potato disease.

Today, several dozen dangerous potato diseases are known that cause significant damage to the crop. One of the dangerous viral diseases is ring rot, which often spreads in small private farms where planting material is rarely changed. This disease develops in tubers only under certain conditions. The causative agent of the disease can be transmitted for years from planting material to a new crop and not appear until favorable conditions occur.

Many gardeners grow potatoes and do not pay attention to the fact that most of their potatoes are infected with this disease. This is due to the fact that only 1-5% of the total crop is affected from the beginning, which allows the gardener to ignore the manifestation of this disease. But over time, more and more crops will be affected by the disease and, accordingly, there will be more and more losses. Therefore, it is very important to know how to effectively deal with the spread of ring rot on potatoes.

Symptoms of the disease

The disease manifests itself both on tubers and on the ground green part of the potato bush. The main symptoms of ring rot are:

1. On tubers, the manifestation of the disease is not easy to notice without violating the integral structure of the tuber, that is, it must be cut. When cutting the tubers, you can see yellow or already brown rings that will cover the area close to the peel.
2. Under favorable conditions, infected tubers can completely rot, while pressing on the tuber will release a slimy mass.
3. External signs of the disease may appear under favorable conditions for the development of the virus in the middle of the tubers. For this, planting material is heated at temperatures from 15 to 18 degrees Celsius.
4. On the grassy part of the potato bush, the disease manifests itself in the period after flowering. At this time, thin stems on infected bushes begin to turn yellow. The leaves also curl and turn yellow. Such stems break out poorly and gradually die off. Such a death is explained by the destruction of the vascular structure of the potato (first the tubers, and only then the stems).
5. When planting heavily infected planting material, some of it will rot in the soil, and some will sprout. Such seedlings will be dwarf and poorly developed. The stems of infected bushes are thin, and the leaves on them are small and close to each other.
6. If from year to year your planting material produces less and less seedlings, it needs to be replaced, since most likely the potatoes are already infected with ring rot.

Conditions for potato infection

The virus persists only in tubers, so infection mainly occurs due to poor-quality planting material or through potatoes left in the soil. The main conditions for infection of potatoes with ring rot are:

1. Poor quality planting material.
2. Transfer of planting material in contaminated containers.
3. Cutting planting material with an infected knife. When preparing planting material (when cutting large tubers), when cutting one infected potato, all seeds can be infected.
4. Planting potatoes in the same place for more than 2-3 years.
5. The disease develops better if the potato is grown in a warm and fairly dry climate. If the summer is wet and cool, then the disease may not manifest itself.
6. Most often, infection occurs at harvest.. If the peel of the tubers is cut and damaged, the virus can penetrate inside and be stored until spring.
7. Potatoes often become infected with the disease when stored improperly.

Fighting methods

There are no special chemical means of combating this disease. Therefore, this disease is considered quarantine. The main measures to combat this disease are:

1. Compliance with the optimal terms of crop rotation (1-3 years).
2. Growing resistant varieties of potatoes.
3. It is obligatory to warm up the seed, for 2-3 weeks, at a temperature of 15-18 degrees Celsius. Tubers can be warmed up, both for storage and before planting in the ground. At these temperatures, the disease is well manifested (soft, black-pitted potatoes), which allows you to select most of the infected tubers.
4. Feeding potatoes with potash and nitrogen fertilizers helps to strengthen the immunity of plants.
5. After flowering, it is necessary to dig up all potato bushes with signs of ring rot infection. In favorable years, for the development of this disease, infected bushes stand out strongly in the garden.
6. Before harvesting potatoes, it is advisable to mow the ground part of the potato bushes, which reduces the likelihood of infection of the crop.

It is quite possible to fight potato ring rot, but this is a lengthy quarantine process. If a significant part of the potato is affected by ring rot every year, then the potato planting areas and planting material must be replaced. You need to buy seeds only from trusted manufacturers who have a license and all the necessary sanitary documents confirming the quality of planting material. This is the only way to completely overcome this disease.

Numerous questions from readers of the "First bed without problems" mailing list (newsletter subscription form - on the right) made me prepare texts about potato diseases. According to the descriptions of readers, very often potatoes suffer from ring rot. I am not a specialist in plant diseases, so I took the text from the Handbook called "Protection of plants in household plots", Agropromizdat, 1985.

A bacterial disease of the vascular system of tissues, accompanied by slow wilting of plants and rotting of tubers.

The disease appears at the end of flowering. Individual branches and stems of plants wither. Tubers are affected by two forms of ring rot: vascular ring rot and pit rot.

Damage to the vascular ring noticeable when the tuber is cut along (the vascular ring has a lemon yellow color). When pressing on the cut, a light yellow mass protrudes from the vessels. Darkening or browning of the vessels with the release of fluid indicates the presence of bacteria in them, and a change in the color of the vascular ring only can be caused by physiological causes or fungal infection. At first, tubers affected by ring rot are no different from healthy ones, but subsequently the core and the entire tuber rot.

Pitted ring rot comes down to the main symptom of the disease - the appearance under the skin on the surface of the pulp of the tuber of yellowish oily small rotting spots. The pulp of the tuber rots, and a hole forms, hence the form of rot gets its name.

The disease is extremely harmful, severely affected tubers usually rot and do not sprout. In addition, in diseased plants, as a result of their general inhibition, significantly fewer tubers are formed than in healthy ones. Tubers are the main source of infection.

Pit rot is the primary form of manifestation of the disease, infection occurs in the fall when potatoes are harvested from the contact of tubers with affected tops, with diseased tubers, and containers. Bacteria from the affected tissue (pits) first penetrate into the vascular ring of the tuber, then, during the germination of the tuber, into the vascular system of the stem. From diseased stems, bacteria enter the young tubers formed by the stolons, in which the vascular ring is affected (the secondary form of the lesion is ring rot). During the growing season, the transmission of the pathogen occurs from bush to bush, it is also possible through processing tools.

For the development of bacteria, high humidity and elevated temperature are favorable (optimal 20 ... 25 ° C). Bacteria of this species are very sensitive to drying, the sun's rays are detrimental to them.

Measures to combat potato ring rot

1) selection of healthy tubers for planting;
2) the introduction of medium rates of nitrogen fertilizers and increased rates of potash fertilizers;
3) planting of varieties weakly affected by ring rot;
4) drying tubers in the light after harvesting;

Pathogen potato ring rot bacterium Corynebacterium sepedonicum. The disease is common in all areas of potato cultivation. The pathogen overwinters in tubers or unharvested plant debris; it does not overwinter in the soil. Wet and warm weather favors the development ring rot. In a season with cool weather, the disease often occurs in a latent form. ring rot affects the underground and aboveground parts of the potato throughout the growing season. In the affected plant, the tops wither and the tubers rot (ring rot). The disease is very harmful, in some years crop losses reach 40%. ring rot potatoes develops slowly. The first characteristic signs of the disease appear towards the end of flowering. Bacteria begin to move from the tubers to the stems, which causes clogging of blood vessels and restricts the flow of water to the tops. The leaves lose chlorophyll and gradually turn yellow and wither, the stems fall to the ground, the whole bush falls apart. The reason for wilting is not only the cessation of the water flow, but also the action of toxins released by the pathogen. Tubers are infected in two ways - through stolons and through damage to the peel. In the first case ring rot potatoes softens the vascular system and when pressed on the tuber, a yellow mucous mass is released from it. In the second, bacteria penetrate the tubers in the autumn during harvesting, and the disease manifests itself only in the spring. In places of defeat, light spots are formed under the peel, the pulp here rots and pits form. If such tubers are planted, then a plant grows with underdeveloped stems and leaves located close to each other. Tuberization in such plants is absent. This type of infection ring rot called dwarfism. Infection potato ring rot It is transmitted during harvesting through agricultural implements, when tubers come into contact with the affected tops, through mechanical damage.

Table 2. Biological features of the development of pathogens of potato diseases

Measures to combat potato ring rot

selection of healthy tubers for planting;

introduction of medium rates of nitrogen fertilizers and increased rates of potash fertilizers;

planting varieties that are weakly affected by ring rot;

drying tubers in the light after harvesting;

sorting potatoes before storage (only dry potatoes are stored).

Measures to combat Fusarium potato:

To prevent the disease, potato seedlings are sprayed with microdoses blue vitriol(2g per 10 liters of water). To protect plants from infection during the growing season, bushes 2-3 times spud, and the last time (before the tops close) is the highest.

The complex of control measures also includes a chemical method. Starting from the phase of closing the tops in rows, potato plantings are prophylactically treated twice (with an interval of 10-12 days) with one of the systemic fungicides: arceridoma(60% w.p., 50 g/10 l water), oxychome(80% w.p., 20 g), Ridomilom MC(72% w.p., 25 g). If the disease manifested itself early, then systemic drugs are used once. In the second half of the growing season (after flowering), treatments are carried out with contact preparations: Ditanom M-45(80% w.p., 20 g), cuproxate(34.5 k.s., 25 g), copper chloride(90% w.p., 40 g) with an interval of 7-8 days. Waiting period 20 days. The consumption of the working solution is 3-4 liters per 100 sq.m. Preparations should be alternated, using one or another fungicide no more than 2-3 times per season. The total number of treatments against late blight (depending on the region) is at least 3-4 ( see also biofungicides)

The best way to combat late blight is to cultivate resistant varieties. There are few of them, therefore, relatively unaffected varieties should be planted in areas of annual development of the disease: Nevsky, Arina, Bryansk novelty, Willow, Spring, Vyatka, Hybrid VKI, Blueness, Detskoselsky, Liina, Loshitsky, Lugovskoy, Mavka, Naroch, New, Spark, Tempo, Sante, September, Tomich and etc.

Proper placement of varieties and crops is of great importance. Planting late-ripening varieties in close proximity to early-ripening and medium-early ones, which are earlier affected by late blight and become sources of infection for late varieties, should be avoided. The best varieties for disease resistance are Valentine, Elor, Red rose, Russian souvenir. The most resistant in terms of tops Master and Mustang, for tubers - Visa and Oredezhsky.

If possible, it is better to place a plot with potatoes annually in a new place, away from tomatoes, which also suffer from late blight.

And finally - what rules should be followed when harvesting potatoes in order to prepare high-quality planting material for the next year.

Firstly, after digging up the tubers, they must be dried: in dry weather - right on the site or in the field, in rainy weather - under a canopy. After 3-4 weeks after harvesting, the tubers should be sorted out again and only after that they should be stored for permanent storage. Sick tubers are easy to distinguish immediately after harvesting: their peel is covered with slightly depressed hard, brown, grayish-lilac and other spots. If such a potato is cut, it is clear that the affected tissue under the stain with brown “tongues” goes deep into the tuber. Weakly affected, with a slightly noticeable spot, the tubers can survive until spring (heavily affected ones will probably rot), but 40-50 days after planting, fungal spores will develop and infect young and healthy shoots, and from them the infection will pass to the shoots. This is why it is so important to discard ALL diseased tubers.

Seed tubers are placed for germination. At a temperature of 16-18 degrees for 20-25 days, spots of late blight and other diseases become noticeable, and diseased tubers are removed. The resistance of potatoes to the disease can be increased by treating the seed tubers before planting. agate-25K ( 7 g/0.6 l per 50 kg) or immunocytophyte(0.3-0.4 g/140-150 ml per 20 kg) by soaking them for 15-30 minutes. Such tubers should be planted immediately after treatment or in the next 1-2 days.

Measures to combat potato cancer:

quarantine measures. It is forbidden to export not only potato tubers, but also planting material of other crops (root crops, bulbs, seedlings of fruit trees) from the centers of the spread of potato cancer, with which the spread of infection is possible. If cancer is found on tubers, it should be immediately reported to the quarantine inspection for special measures to be taken.

The use of potatoes infected with cancer for livestock feed is allowed only in boiled form, since winter cysts that have passed through the digestive tract of animals when raw potatoes are fed do not lose their viability and the infection can then spread with manure.

On soils infected with cancer - cultivation of only cancer-resistant varieties (Berlichingen, Iskra, Belorussky early, Priekulsky early, Table 19, Gatchinsky, Smachny, Temp, Kameraz, Loshitsky, Ekaterinsky, Druzhny).

The introduction of high rates of organic fertilizers for potatoes. Cultivation of potatoes after corn, lupine, cabbage, millet, wheat, which contributes to a more rapid self-purification of the soil from cancer zoosporangia.

Destruction of new foci of potato cancer found in areas where there was no disease before, by thorough disinfection of the soil (performed by special organizations of the quarantine service). Nitrafen (400-440 g in 20 l of water per 1 m2), urea (1.5 kg/m2), preparation 242 (150 cm3/m2) are used for soil disinfection.