Potato blackleg disease control measures. Black leg of potato: causative agent, causes and methods of prevention. How to treat potatoes from fungal infections

Which we talked about in our previous articles. But, unfortunately, that's not all. potato disease that threaten your crop.

Therefore, it is very important to know what other diseases can affect potatoes, how to avoid them and how to deal with them. It is to this topic that our today's article will be devoted.

potato rhizoctoniosis

Why is Rhizoctonia dangerous?

This - fungal disease of potato that affects stems, roots, stolons and sprouts. It looks like dense dark lumps on the tubers, and on the sprouts - brown sores that grow and destroy the sprouts. Potatoes affected by this disease lag behind in development, fade ahead of time. In advanced cases, the upper leaves of the plant turn red, curl, air tubers form on the stem.

The most common source of this potato disease soil and infected tubers serve.

If no measures are taken, rhizoctoniosis can destroy 15-20% of the crop.

How to deal with Rhizoctonia?

Here it is important to control that a crust does not appear on the soil. The probability of hitting this potato disease drops if you plant sprouted potatoes in warm soil. Before it is treated with a 1.5% aqueous solution of borax or boric acid.

Potato rot

Wet rot of potatoes

This potato disease manifests itself during storage - the tubers are moistened, softened, gradually turning into a mass of pinkish or brownish color. Increased air humidity, as well as potato susceptibility to other diseases, contributes to the spread of soft rot.

Dry rot of potatoes

It also appears during storage. Sick tubers have voids inside, and on top they are covered with a dry peel with a touch of yellow, pinkish or white.

How to deal with rot?

Since both dry rot and wet rot occur as a result of damage during harvesting and transport of potatoes, the only measures are preventive measures. Care should be taken to harvest the crop, dry it well before storage and give preference to varieties that are resistant to this disease.

Potato Alternariosis

Why is Alternariosis of potatoes dangerous?

This potato disease poses a danger to both tubers and stems, leaves and petioles. At first, dry brown spots appear on the leaves, which grow over time. As a result, the leaf dies off, then the stem is covered with rotting gray-brown ulcers.

How to deal with Alternaria?

Firstly, observe crop rotation and do not plant potatoes next to tomatoes, which are also prone to Alternaria disease.

For prevention, increase the amount of phosphorus and potash fertilizers. Spraying with Bordeaux liquid (1%), polycarbicide (40 g per bucket of water), copper oxychloride (40 grams per bucket of water), arceride (50 grams per bucket of water) also helps. It is best to alternate these drugs - then there will be no addiction disputes to a particular drug.

potato scab

Why is potato scab dangerous?

Scab is potato disease, which manifests itself in the form of dry ulcers on potatoes, especially young ones. Scab-affected tubers have poor germination, rot at. Most often, scab affects potatoes growing on sandy soils.

The scab itself is the simplest actinomycete organisms, which occupy an intermediate position between the simplest fungi and bacteria. It develops in straw, on plant debris, while infecting potatoes and soil. Feels especially good with excess and fresh manure in the soil.

How to deal with potato scab?

Forty percent formalin (0.5 l - per 100 liters of water). To do this, a wicker basket with potatoes is lowered into a barrel with a solution for a couple of minutes, then it is allowed to drain, poured onto a bedding, covered with a tarpaulin and kept for another 2 hours.

The development of scab can be restrained if fertilizers are used, which are potassium magnesia, superphosphate (30 grams per 1 "square"), ammonium sulfate (40 grams per 1 "square").

potato cancer

Why is potato cancer dangerous?

Potato cancer is a dangerous quarantine disease. If it hit your site, you will have to destroy all the tubers.

This potato disease manifests itself in the form of growths that slightly resemble cauliflower. They increase over time. Potato cancer can affect both tubers, and the root collar, and potato stolons. Over time, white growths turn brown, increase, turning into a mass of mucous consistency.

Potato cancer is transmitted with infected tubers, manure, streams of rainwater, tillage tools.

How to deal with potato cancer?

Unfortunately, effective means to combat potato cancer have not been developed. The only thing that can be done is to use those that are resistant to this disease.

Black potato leg

Why is the black leg dangerous?

With this potato disease dark spots appear on the lower part of the stem, the leaves curl, turn yellow, the stem fades. Tubers are infected through stolons, which soften and rot in the affected areas.

Infection of potato tubers with this disease occurs most often during harvesting, through diseased tops or before planting - when cutting seed potatoes.

How to deal with the black leg of potatoes?

The fight against this disease is quite complicated and consists of a number of complex measures: germination of seed material, removal of dry potato stems before, gardening and drying of tubers before storage. If the black leg still struck your crop, diseased bushes are removed from the site and destroyed.

Potato ring rot

Why is ring rot dangerous?

This potato disease is activated in the second half of the growing season, when the plant blooms. In the bush, the stems gradually die off - they fall to the ground, and inside they are filled with yellowish mucus. The disease spreads to the tubers, they become covered with pinkish or brownish spots and cracks. If you cut such a tuber, it turns out that under the skin the potatoes are softened and rotten.

How to deal with ring rot?

Infection of this potato disease occurs only through infected tubers, so planting material should be monitored and diseased potatoes should not be used. Since the disease can be transmitted when cutting seed potatoes, disinfect the knife with formalin or lysoform after each potato.

Tatyana Kuzmenko, member of the editorial board of the Sobcorrespondent of the online publication "AtmAgro. Agroindustrial Bulletin"

Potato, as one of the most popular vegetable crops, is grown in almost all regions, both in the northern and southern regions. To obtain a quality crop, the main thing is to create favorable conditions and respond to pests in a timely manner. Describing common potato diseases and treatments will allow the gardener to spot the problem and take appropriate action.

The main causes of potato diseases

Despite all the resistance of the culture to negative environmental factors, it is often affected by various fungi, viruses and bacteria. In conditions of high humidity, potato diseases develop quite quickly and can cause significant harm to the entire farm. In the absence of proper treatment and the omission of the initial stage of development, the plants die, the marketable qualities of root crops deteriorate. Such dangerous diseases include late blight, scab, blackleg, rhizoctoniosis, cancer, soft rot of tubers and conditions caused by viruses.

Fungal diseases of potatoes

Most of the fungi can also affect other agricultural plants. Therefore, it is necessary to become more familiar with potato diseases and be able to deal with them.

common scab

A clear sign of this potato disease is the presence of brown spots on the peel, which gradually increase in size, the integrity of the peel is broken and small ulcers 5-10 mm in diameter are formed. After some time, they merge, capture most of the tuber, the formation of a continuous flaky crust is observed.

The causative agent of the infection is found in seed material, contaminated soil. Therefore, it is recommended to take healthy root crops for planting, use resistant varieties (Bulletin, Resurs, Pamir, Sokolsky, Kariev, etc.), observe a crop rotation of 4-5 years, treat tubers and soil with Trichodermin, a drug that reduces the risk by 60-80% development of this disease. It is also useful to spray root crops with Maxim, Tekto, TMTD before storing.

powdery scab

Potato disease is actively developing in conditions of heavy precipitation. It affects the root system of plants, stolons, tubers. As a result of the vital activity of fungi, growths of various shapes and sizes appear on all parts of the bush. At first they are white in color, and then they turn dark in color and eventually disintegrate. Red sores 5-7 mm in size are observed on root crops.

In order to prevent the appearance of powdery scab, it is necessary to observe crop rotation, plant only healthy specimens, adhere to the correct agricultural practices, and promptly replenish the missing macro- and microelements. Effectively carry out liming of acidic soils to reduce the likelihood of disease.

It is imperative that before laying root crops for storage, treat them with 3% bleach or a 5% solution of copper sulphate. Before planting in the ground, the seed material is treated with TMTD preparation for 2 weeks, the consumption rate is 2.1-2.5 kg/t.

You can prevent the appearance of silver scab on the site by planting only high-quality seed potatoes. Crop rotation is a must. Root crops must be thoroughly dried before storage. In the cellar, the optimum temperature is 1-3 degrees. Root crops are processed with Maxim, Titusim. Such procedures are advisable 3 days after harvest. Before planting in the ground for 15 days, it is necessary to pickle the seed material with TMTD.

Black scab (rhizoctoniosis)

The causative agent of the disease settles on planting material. As a result of harmful activity, root crops, stem and stolons are affected. Young plants, which often die, cannot resist him. Due to the high spread rate of black sclerotia, a significant part of the plantings is endangered. The disease is determined by deep spotting and net necrosis. The reason for the development of the fungus is high humidity and air temperature above 20 degrees.

Periodic checks of seed material for the detection of pathogenic microflora can reduce the risk of infection of the future crop. Before laying the tubers for storage, it is necessary to spray with special preparations. When a fungus is detected, treatments are carried out with Fitosporin, Mancozeb, Phenoram Super, Kolfugo.

Dry spotting (alternariosis)

Potato disease develops mainly in dry and hot weather. Its main features are numerous brown spots on the foliage, similar to fingerprints. If no action is taken, the leaves dry out, the tubers become smaller, and yields decrease. The causative agent of the disease is a fungus that settles on plant debris. It can infect tomatoes, peppers, eggplants.

To combat Alternariosis, chemicals are used: Quadris, Ridomil Gold, Bravo, Oksihom, Integral. A high protective effect is observed during preventive treatments.

Not only root crops, but also the aerial part of the bushes are at risk of infection. Pathogenic microorganisms can be detected by tubercles on potatoes near the eyes. This is the initial stage of the disease, later the growths increase in size, having an arbitrary shape. The risk of damage increases if this crop is planted in the same area for 4-5 years. The spread of the fungus throughout the garden occurs through inventory, shoes.

Given that this is an incurable disease, it is recommended to purchase more resistant potato varieties for planting. A crop affected by cancer must be completely destroyed. You cannot eat it.

Dry rot (fusarium)

This disease is dangerous during the entire growing season of the crop, but especially before the flowering phase. Contributes to its development intensive evaporation of moisture in hot weather. Damage to farming can reach almost 40%. The characteristic symptoms are the loss of turgor in the leaves, the coloring of their edges in anthocyanin color. In this case, the color of the upper leaves becomes lighter. The color of the stem changes to brown, with excessive moisture it rots and becomes covered with an orange (pink) bloom from the spores of the fungus. The wilting period of diseased plants is 2-4 days.

To prevent dry rot on potatoes, crop rotation must be followed. Grow exclusively varieties with a high degree of resistance, with strong immunity. Planting material must be absolutely healthy and treated with TMTD.

late blight

It is necessary to know the description of this disease, since it spreads rapidly and is capable of destroying all plants in just a couple of weeks if you do not react in time. The disease spares neither stems, nor leaves, nor root crops. Its manifestations are considered dark spots with a border in the form of a white coating. In dry weather, the foliage dries out, and in wet weather it rots. In 4-5 hours, the fungus can spread throughout the plantation through water during irrigation, precipitation, and gusts of wind.

When the bushes reach a height of 20 cm, it is necessary to treat the tops of potatoes with a solution of copper sulfate, prepared at the rate of 10 g of the drug per 10 liters of water. A solution of 1% Bordeaux liquid also helps, based on 400 g of the product per 10 liters of water. With a strong lesion, the procedures are carried out 4 times with an interval of 7-10 days. Of the agrochemicals, Arceride works against this pathogen.

fomoz

With the development of the disease, elongated spots are formed, on which pycnidia appear. After some time, they completely discolor. The fungus shows its activity in the second half of the growing season, affecting the stems, and during storage of tubers. In most cases, voids are formed in the pulp, on the surface of which there is a gray coating of mycelium, but there may be dark-colored pycnidia.

Measures to combat the disease are to observe crop rotation, to prevent mechanical damage during harvesting and during transportation. Seed potatoes are to be treated with Maxim agrochemical before being stored in storage. After spraying, the root crops should be well dried.

Viral diseases

About 20 viruses are capable of reducing the productivity of this crop, each of which has its own characteristic manifestations. Pathogens cause the greatest damage 2-3 years after the defeat. The problem of their destruction lies in the fact that the infection remains inside the plant in a latent form, in addition, viruses are carried by various insects over long distances. In order to effectively deal with diseases and pests of potatoes, you need to know in what period they are activated and what drugs are able to resist them.

Mottled or ordinary mosaic

A photo and description of potato viral diseases greatly simplifies their detection in a personal plot. So, a simple mosaic can be identified by the appearance of regular-shaped spots with light green patches. In some cases, the virus may appear as black spots of dead tissue. Its carrier is a sucking insect, and its source is plants of the nightshade family (tomato, nightshade, henbane, dope, etc.).

As soon as the first signs of the disease were detected, it is recommended to treat with Quadris, Revus. Experienced gardeners for planting use varieties with high immunity.

striped mosaic

A characteristic symptom of this potato disease is the appearance of spots in the form of rectangular stripes or located in a chaotic manner. The number of strains of this mosaic is quite large, which complicates the identification process.

As a result of the activity of the pathogen, the stem of the plant becomes brittle and often simply breaks under its own weight. Yellow-brown spots appear on the underside of the leaf plate and on the veins. It is necessary to fight with a striped mosaic with a fungicide such as Shirlan, Bravo. Conduct spraying plantings.

With potato wrinkle disease, a diseased plant stops the growing season a week earlier than healthy specimens, which affects yield indicators. After identifying the affected bushes, it is necessary to treat the leaf with the fungicide Ridomil or Ditan.

Rustling mosaic

Two types of viruses can cause the disease - M and L. When the first one is affected, the leaves of the potato twist up. At the same time, mosaic and curliness can complement this infection. If the source of the disease is the L virus, twisting is observed along the central vein. It can be either spoon-shaped or helical twisting.

Regardless of the type of pest, leaf plates become hard and rustling, and net necrosis is clearly visible on root crops. A change in the shape of the leaves may occur due to infection of the bushes with fungi.

It is almost impossible to cure diseased plants; it is advisable to purchase high-quality seed material with a high degree of resistance to such diseases.

Stolbur

Phytoplasmosis, as this disease is also called, is caused by mycoplasmal bodies. It is south and north. In the first case, the internodes are shortened in plants, the upper leaves are reduced in size, a yellow border appears along the edges, axillary leaves grow in breadth. After some time, due to the death of the root system, the bushes wither and die. On diseased root crops during storage, you can see long, colorless, filamentous sprouts. The carrier of the disease are sucking insects (cicada).

The northern stolbur of potato manifests itself in the form of a slow growth of bushes, which branches, and the flowers turn green and smaller. To prevent the development of this dangerous disease, it is necessary to select planting material only from healthy plants.

This is a tuber disease caused by TRV. It manifests itself in the form of spots with rot, rings, arcs, dark stripes. When the fetus is cut, foci with a rotten edging and creamy filling in the form of mucus with an unpleasant odor are found. Yield losses can be up to 45%. You should not eat such root crops.

Here, chemicals and folk methods are powerless. The only way out is to observe crop rotation and select resistant varieties for planting.

The causative agent of the disease is the PSTVD virus. Under its influence, deformation of tubers is noted, the commercial qualities of the crop are lost. The disease can be identified by the anthocyanin coloration of the edges of the leaves. Similar staining is observed on the root crops themselves. Considering that during the Gothic, root crops change their shape significantly, for planting in the ground, you need to take only the material of the correct shape. The spread of the virus occurs mechanically or by contact, through insects.

To reduce the likelihood of the development of spindle-shaped root crops, it is necessary to perform basic agricultural practices (crop rotation, weed control, etc.), carry out insect treatments, plant green manure crops, disinfect vegetable stores and inventory.

Bacterial diseases

It is rather problematic to diagnose and cure bushes affected by bacteria in time, since they are present on the culture in the form of latent infections. They do not manifest themselves in any way, but in the end the potatoes rot. To prevent bacterial diseases of potatoes, it is recommended to protect them during transportation in order to minimize the appearance of mechanical damage, collect them on time and apply mineral compositions in a timely manner.

Brown bacterial rot

Bacteriosis on plants appears only the next year after planting. Infected root crops are able to grow and develop, but the bushes turn out to be weak, lose turgor and quickly wither. Signs of brown bacterial rot on potatoes are oblong stripes on the veins and basal part of the plant. When the stem is cut, mucus is observed. The leaves change shape, lose their green color and curl.

Before planting, only healthy seed material should be selected. Be sure to etch with TMTD or Planriz.

You can see the damage with a longitudinal section of the tuber. With ring rot, an unpleasantly smelling mass of light yellow color is released from the potato. After some time, the root crop rots. For the purpose of prevention, equipment should be treated with disinfectant compositions, in particular, with a solution of potassium permanganate. It is possible to increase the resistance of plants with the preparation AGAT-25K.

wet rot

Moist and soft to the touch spots appear on the surface of the roots. Infection occurs as a result of mechanical irritation of the skin with microbes and other diseases. The flesh becomes watery, dark brown in color. Potato soft rot can be prevented by treating seed material with antifungal and antibacterial agents.

Mixed internal rot

A disease appears on potatoes with mechanical damage. Through cracks in the peel, bacteria, fungi penetrate inside and provoke decay. Therefore, in order to prevent the development of potato rot, the cellar should be pre-treated with a solution of copper sulfate and cleaned of plant residues. Be sure to inspect the root crops.

Most often, infection occurs when a crop is planted in place of cabbage. With a black leg, the potato becomes wet, the lower part of the stems rots, which leads to a decrease in yield. The leaves on the bushes turn yellow, wither. Control measures are the same as for other types of bacteriosis.

With the development of glandular spotting, mottling is observed in spots on the pulp. Their color can be from light amber to dark brown. The shape is wrong, the edges are blurry. The reason lies in dry weather against the background of excessive amounts of iron and aluminum. The leaves are practically not affected, this is a disease of the pulp.

Preventive measures

First of all, you should choose resistant varieties of potatoes. At the first signs of infection of the bushes, carry out appropriate treatments, follow the rules of crop rotation. Planting care should be timely, especially when it comes to watering, hilling, top dressing. Only prevention will prevent potato diseases and save the harvest.

A black leg on a potato is often a sign of disease. You can easily distinguish traces of excessive watering from plant disease by simply looking at it.

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

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

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

Microorganisms E. Carotovora can be seen under a microscope. The bacterium has short sticks, straight, with rounded edges. The average size is 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, does not form capsules and spores. They are gram-negative, facultative anaerobes.

It is possible to diagnose and perform prevention against the disease at the stage of planting the crop. To do this, let's move on to the symptoms and pathogens of the disease.

Symptoms and pathogen

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

Affected plants look much worse than healthy counterparts: the appearance is oppressed, the color of the foliage changes, the leaves can be stunted yellow and twisted.

In the bush, individual shoots may be infected, but the entire course may wither at once.

A striking sign of the disease is the decay of the roots of the plant and the blackening of the legs. In view of this, additional roots cease to develop.

If you try to pull out an infected plant from the ground, even a child will easily succeed, since it is extremely easy to pull out a plant.

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

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

Outwardly, you can inspect the tubers and notice small dark spots, this darkening spreads inward. The affected fetus darkens and turns into an unpleasant mucous mass. The rot is present on the outside of the tuber and inside the fruit. Outwardly - rotten and slimy mass, inside - weeping black and uneven edges.

Diagnosis of infection

Having examined the stolon part, you can even notice changes with the naked eye. The bacteria spread by moving from stems to daughter tubers and, spreading to the middle, turn 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 the affected tubers is an unpleasantly smelling liquid that flows from the cracks. Cavities are formed inside the tuber, externally - the presence of cracks, dark peel.

In dry conditions, the infection proceeds in a chronic form.

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

The rapid development of the disease. The period is from 4 to 6 days. Wednesday - 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 the plants are easily pulled out of the soil. Additionally, browning of the vascular bundles is present on transverse sections.

Causes of infection

Biology of blackleg

Black leg - affects not only potatoes. It can also be found in other cultures. Lettuce, cabbage, radishes and horticultural crops are at risk. The signs of infection in these plants are exactly the same: the stem rots, the plant withers and changes the color of the leaves.

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

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

Fighting methods

Preventive measures against blackleg. Biological agents

Preventive measures against Blackleg. Chemicals

• Tubers are sprayed before planting 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: foundationol, vitaros, topsin-M, bental or previcur in the proportion of 2 grams of the drug per 1 liter of water.
• For prevention, watering is used with the addition of "Effekton" in the proportion of 3 tablespoons per 10 liters of water. Consumption per plant - half a liter of water. The solution must be heated to a temperature of twenty-five degrees.
• Before storage, potatoes are treated with Maxim.

Review

Anastasia

We decided to grow potatoes where they grew last year. They thought it was all nonsense and there would be no problems. It was not there: the potatoes, even during the shoots, began to turn into something incomprehensible. It turned black and dark, we already thought we wouldn’t save it, but a neighbor suggested a good drug Energen, they treated it and everything seemed to go away.

Pathogen: Pectobacterium carotovorum subsp. atrosepticum (van Hall) Hauben.

Maliciousness. The black leg of the potato is ubiquitous in growing areas cabbage. Affected young plants rot in the lower part of the stem, and wet rot of tubers also forms on their tubers. As a result of the development of the black leg of potatoes, plantings become thinner, productivity decreases, seed and commercial qualities deteriorate during storage. Yield losses depend on the aggressiveness of the pathogen and weather conditions and range from 1-2 to 50-75%. For example, if 5% of plants are affected by the black leg of potatoes during the growing season, then the losses will be 20% or even more during the storage period.

Symptoms of a black leg of a potato

As a result of the early development of the disease, the lower leaves of the seedlings turn yellow, the leaves become stiff and curled in a boat. The growth of the upper leaves occurs at an acute angle, later they also turn yellow. The base of the stem becomes soft, rots, when pulled out of the soil, it easily comes off in the region of the root collar.

Tubers are affected starting from the second half of the growing season. Affected tubers soften at the point of attachment to the stolon. At first, the softening is light yellow or colorless, later the core of the tuber rots, starting from the stolon part. As a result, the tissue darkens, becomes soft, slimy, acquires an unpleasant odor. During storage, tubers affected by the black leg of potatoes become a source of wet rot.

Black leg of potato photo:

Biology of the black leg of the potato

Potato black leg bacteria secrete pectolytic enzymes that cause soft rot, maceration and mucus. The penetration of bacteria into tubers occurs through damaged tissue, stolons and lenticels. The disease is spread by insects. The greatest harmfulness of the black leg of potatoes is observed at high humidity on heavy soils. However, there were cases when the black leg of potatoes and wet rot, under the condition of wet weather, developed well on sandy loamy soils.

sources of infection. The source of infection can be planting material and plant residues until they completely rot.

Protective Measures Against Blackleg Potatoes

It is important to observe crop rotation, to carry out a thorough incorporation of plant residues. Potatoes before laying in storage in the fall and before planting in the spring must be carefully sorted out. In the event of a disease, in the following years, grow only resistant varieties such as: Gatchinsky, Priekulsky early, Borodyansky, Volzhanin, Iskra and others.

biological agents. In order to reduce the infection of tubers with wet rot, the seed material must be treated with a working solution of the Fitosporin-M preparation at a rate of 0.4-0.5 kg before planting, after dissolving it in 30 liters of water, spraying is carried out with tubers mixing.

Chemical means. Dressing of seed tubers before planting with TMTD, VSK. The working solution is prepared in this way: 4-5 liters of the drug are dissolved in 65-70 liters of water and 1 ton of tubers are treated. It is possible to use other drugs of this group.

Before laying seed potato tubers for storage, they are pickled with Maxim. Preparation of a working solution: 0.2 l of the drug is dissolved in 2 l of water and the tubers are sprayed, stirring them from time to time.

Introductory explanations.

Diseases such as cancer, late blight, black scab of tubers, macrosporiosis and others cause great damage to potato growing. The causative agents of these dangerous potato diseases are fungi. In addition to fungi, potatoes are affected by actinomycetes, bacteria and viruses. The harmfulness of potato diseases is manifested not only in a decrease in crop yield, but also in a decrease in the commercial value of tubers (deterioration in taste, increased waste of ware potatoes, and a decrease in the keeping quality of tubers).

Black potato leg - a bacterial disease. Pathogen - Pectobacterium phytophtorum.

The black leg appears both on tubers and on plants in the field. In affected plants, rotting and blackening of the base of the stem occurs. The leaves on such stems first become chlorotic, then turn yellow and dry. Affected stems are easily separated from the mother tubers and pulled out of the soil. The disease appears early, sometimes shortly after emergence.

On tubers, the blackleg is manifested by core rot, which almost always begins at the point of attachment of the tuber to the stolon.

Sick bushes differ from healthy ones: they form a small number of stems (2-3 pieces). The leaves of diseased plants become mucilaginous in wet weather, brown spots and cracks appear on them, and if you make a cross section of the stem, then the blackening of the vessels is clearly visible, because. bacteria clog the vascular system of the plant.

The blackleg bacteria persist and spread mainly with planting material. In the field, the infection persists only until the plant residues rot, and bacteria that enter the soil directly are quickly suppressed by other soil organisms. Air temperature 15–18 0 C and high soil moisture contribute to the development of the disease.

The disease is spread by soil insects: larvae of horn beetles, putrefactive flies and biting cutworms.

Control measures: healthy tubers are selected for planting, weighing no more than 50 g; before planting, potatoes are germinated and tubers with weak sprouts are discarded; carry out phytosanitary cleaning of potato plantings; when harvesting potatoes, they try to prevent contact of the tops with tubers and mechanical damage to tubers; apply fungicides permitted by the "List ...".

ring rot - a bacterial disease caused Corynebacterium sepedonicum.

The disease manifests itself in plants during the growing season in the form of wilting, which manifests itself in the middle or in the second half of the growing season. Most often, the leaves turn yellow and fade not on the whole plant, but on individual stems of the bush. A cut through the affected stem shows darkening of the vascular system of the stem. When pressed, viscous yellowish mucus comes out of the infected vessels - an accumulation of bacteria.

On tubers, the disease manifests itself in two forms: the first is tuber ring rot and the second is tuber pit rot. In the first form, the manifestation of the disease is marked by the formation of a continuous or intermittent brown ring, which is found on a cut made through a tuber. The vascular tissue affected by bacteria softens, and when pressed, droplets of a whitish mucous mass protrude from it.

Pitted rot is characterized by the formation of yellowish, at first, as if oily, rounded spots under the skin of the tuber. Spots of pitted rot are found only when the tuber peel is removed.

The infection persists in the seed material. When planting from diseased tubers, diseased shoots appear, and on the cut of the stems, an accumulation of bacteria along the vascular ring is visible. Nutrients and water do not enter the plants. Therefore, in diseased bushes, the leaves dry up and wither, and the number of stems grows to 2-3.

Control measures: removal during phytocleaning of diseased plants. Timely harvesting (when the tubers are ripe and the peel has coarsened), if possible in dry weather. Culling of diseased tubers when cutting planting material. Apply fungicides permitted by the "List ...".

Wet rot of potatoes. causative bacteria - Pseudomonas, bacillus, Pectobacterium and etc.

The disease manifests itself on tubers, which are light at first, later becoming dark brown. With the further development of the disease, the tubers become soft and wet, and their pulp turns into a mushy mass with an unpleasant odor. The affected areas are covered with yellow-brown mucus, but the peel often remains intact.

Control measures: haulm mowing 7-14 days before harvest; prevention of mechanical damage to tubers; drying tubers after harvesting and creating optimal storage conditions; the use of fungicides permitted by the "List ...".

Dry rot of potatoes. The causative agents of the disease are fungi of the genus Fusarium (Fusarium coeruleum saac., F. Sambucinum Fuck., F. solani App. et wr. , and other species) that belong to the class Deuteromycetes order Hyphales.

The disease is found on tubers approximately in the middle of storage. The tissue affected by the fungus becomes dry and rotten, the peel on the tubers in the affected areas shrinks and acquires a characteristic folding. In the future, the rot covers the entire tuber, it shrinks, becomes hard. The surface of the tuber is covered with a bloom of mycelium and pads of conidial sporulation of the fungus, which can be white, yellow or pink. The infection persists in the soil.

Control measures: prevention of mechanical damage, hypothermia or self-warming of tubers during harvesting and transportation; thorough and advance (1.5-2 months) cleaning and disinfection of the storage; light hardening of seed potatoes before storage; storage of healthy tubers; the use of fungicides, according to the "List ..."; compliance with the storage regime.

Phomosis, or button rot of tubers. Pathogens: Phoma exigua Desm. ( Class Deuteromycetes, order Sphaeropsidales) , Ophiobolus porphyrogonus Sass. (Class Ascomycetes, subclass Loculoascomycetidae, order Pleosporales) .

The disease manifests itself in the formation of rounded, somewhat depressed spots on the tubers. On the section, the tissue under the stain is brown, almost black along the edges. The affected tissue shrinks and cracks over time. Pycnidia protrude through the skin of the tuber. On the stems during flowering, near the petioles, blurry spots elongated to 8 cm are visible, on which many light or dark brown pycnidia subsequently form. Sometimes the spots take on the character of ulcers, their edges are distinguished by a darker color. The stems lag behind in growth and wither, and with a strong defeat they break. Infection of the tuber can occur again in the field during the storage period.

Control measures: implementation of quarantine measures; compliance with crop rotation; planting healthy tubers; pre-harvest haulm mowing; creation of optimal conditions for storage of tubers; the use of fungicides according to the "List ...".

Late blight of potatoes. Pathogen: Phytophthora infestans(Class Oomycetes, order Peronosporales) .

Late blight is one of the most common and harmful potato diseases. For the development of the fungus, it is necessary to have drops of water that remain after dew or rain on potato leaves, and an air temperature of 19-24 C. The development and spread of the disease increases if the temperature drops to 10-13 C at night.

The disease appears in the mass before flowering. Blurry dark brown weeping spots appear on the edge of the leaf blade. On the underside of the leaves, on the border of the affected and healthy tissues, a white coating is formed, which is clearly visible in rainy weather or in the morning before the dew dries. On the stems and petioles, elongated brown stripes are formed, on the tubers - slightly depressed, sharply defined brown hard spots. On the cut of the tuber, a rusty coloration of the pulp is visible, distributed in depth in the form of separate sections, the so-called tongues.

Tubers are mainly infected with fungal spores washed off by rain or dew from the leaves and penetrating through the topsoil. Many tubers are affected during harvesting in contact with diseased tops.

The infection persists as mycelium on tubers and as oospores on plant debris or in the soil.

When planting diseased tubers, brown sprouts appear, which often die. From these single foci of infection, the fungus spreads by rain or wind to neighboring plants. In addition, sporulation of the fungus is formed on the affected tubers that have fallen into the soil during planting, and as a result, the soil around the tubers becomes infectious. Sprouts emerging from healthy tubers planted next to diseased ones become infected upon contact with infected soil.

Control measures: mowing tops 1.5-2 weeks before harvesting, selecting healthy tubers for planting, timely high hilling, fertilizing, harvesting in dry weather and laying for a period of 3-4 weeks for temporary storage, and then harvesting sorted potatoes for permanent storage , light hardening of seed potatoes (solanine formed in tubers in the light protects them from rot), the use of fungicides, according to the "List ...".

Potato macrosporiosis . Pathogen: macrosporium solani(Class Deuteromycetes, order Hyphales) .

Macrosporiosis, or early spotting, is manifested by dry, brown, zonal spots on leaves and stems before budding. On the underside of the spots, a black coating forms in the form of concentric circles. Plaque is conidial sporulation. Gradually, the affected leaves turn yellow and dry out. The spots on the stems are the same, but dark brown in color and also with concentric circles. The infection persists as mycelium on plant debris. The harmfulness of the disease is especially high in hot summers with small (short-term) rains or night dews.

Control measures: deep plowing of crop residues, crop rotation, fertilization. Spraying potatoes during the budding period or when the first signs of macrosporiosis appear with fungicides allowed by the "List ...".

Rhizoctonia, or black scab of potatoes - pathogen Rhizoctonia solani, Class Deuteromycetes, order Mycelia sterilia.

On tubers, the disease manifests itself in the form of small, mostly flat sclerotia of the fungus adhering to the surface of the tuber, resembling lumps of dirt. For seed potatoes, rhizoctoniosis is the most dangerous type of scab. On tubers planted in the soil, sclerotia germinate into mycelium, which causes infection of the sprouts. Dark depressed spots form on them, often merging and covering the sprouts with a ring. Diseased sprouts sometimes die before reaching the surface. This form develops especially strongly during early and deep planting of tubers in damp and insufficiently warmed soil, during cold and protracted spring. On adult plants, rhizoctoniosis manifests itself in the form of the so-called white leg. The lower part of the stem is covered with a whitish-gray film formed by the basidial stage of the fungus. Basidiospores from the stem can be washed off by rain into the soil and infect young tubers. Mass infection of a new crop also occurs due to sclerotia in the soil.

Control measures: observance of crop rotation; optimal time for planting tubers with embedding to a depth of 6-8 cm on heavy and 12-15 cm on light soils; when a crust is formed on heavy floating soils, harrowing is carried out 4-5 days after planting and after germination; destruction of weeds (thistle, quinoa, etc.); the use of fungicides permitted by the "List ...".

Potato cancer. Pathogen: Synchitrium endobioticum(Class Chytridiomycetes, order Chytridiales) .

The disease manifests itself on tubers in the form of growths of various shapes and sizes. Very rarely there are growths on the lower part of the stems. With a strong defeat, the entire tuber is covered with growths and loses its commercial value. The growths are destroyed over time and turn under the action of bacteria into a slimy, unpleasantly smelling mass. On a section through the growth, resting spores, or cysts, characteristic of the causative agent of cancer, are found mainly along the periphery of the growth - rather large, oval with a thick thickened shell. Cysts are the dormant stage of the fungus in which it persists in the soil. Cysts can persist in the soil for up to 10-13 years or more. Cysts germinate into the sorus of the zoosporangium with zoospores and cause re-infection in the same summer.

Control measures: cultivation of cancer-resistant varieties, in the focus of potato cancer, plants not affected by this disease are cultivated and the soil is cleared of infection (cabbage, carrots, cucumbers), compliance with quarantine measures, pre-sowing dressing of tubers with drugs permitted by the "List ...".

Common potato scab. The causative agents of the disease are various types of actinomycetes: Actinomics scabies, Actinomicestricolor, Actinomics cretaceus.

On the surface of the tubers, rounded, flat or slightly convex, star-shaped warts are formed. Sometimes cracking ulcers are formed on the surface of the tubers pressed into the tuber. Warts and ulcers often coalesce, covering the entire tuber in scabs. On dug out tubers, a white cobweb plaque of mycelium is noticeable; when the tuber dries, the plaque dries quickly and disappears.

When plants are damaged, there is a decrease in the commercial value of tubers, a deterioration in taste (the starch content is reduced by 5-30%), an increase in ware potato waste, and a decrease in the keeping quality of tubers. The infection accumulates mainly in the soil on plant residues after harvest. Under normal storage conditions, the infection persists in small quantities.

Control measures: observance of crop rotation; cultivation of resistant or slightly susceptible varieties; it is not recommended to place potatoes on highly calcareous soils; on alkaline soils, apply physiologically acidic fertilizers (superphosphate, etc.); presowing dressing of tubers is carried out with preparations permitted by the "List ...".

Glandular spotting, or rustiness of tubers .

This is a non-infectious disease of tubers, found only on the cut: rusty spots of various sizes and shapes form in the tuber pulp.

The manifestation of glandular spotting may be associated with excessive accumulation of iron and aluminum in the plant with a lack of calcium, with increased activity of oxidative enzymes in the tuber and insufficient phosphorus nutrition of the plant. Overheating of the soil enhances the manifestation of the disease.

Control measures: depending on the cause of the disease, protective measures are also built. In some cases, this is the introduction of optimal doses of phosphorus fertilizers, in others - nitrogen fertilizers, and liming is carried out on acidic soils. The normal humidity regime has a positive effect.

1. To study the symptoms of the manifestation of potato diseases.

2. Consider herbarium and collection material, identify diseases, record the progress of the definition in Table 10 and draw the external signs of potato diseases.

Table 10 - Characteristics of pathogens of potato diseases.

3. Prepare preparations, consider and draw pathogens of dry and wet rot of potatoes, late blight of potatoes, resting spores (cysts) of the causative agent of potato cancer.

4. Prepare and examine under a microscope plaque from potato organs affected by macrosporiosis, draw conidiophores with conidia.

5. Prepare a preparation and examine under a microscope sclerotia from a potato tuber affected by rhizoctoniosis.

Control questions:

1. What potato diseases are caused by fungi? What potato diseases are caused by bacteria? What potato diseases are caused by actinomycetes? What potato diseases are caused by viruses?

2. Black leg of potato and measures to combat the causative agent of the disease.

3. Late blight of potatoes and measures to combat the causative agent of the disease.

4. Potato ring rot and control measures against the pathogen.

5. Potato cancer and measures to combat the pathogen.

6. Dry rot of potatoes and measures to combat the causative agent of the disease.

7. Wet rot of potatoes and measures to combat the causative agent of the disease.

8. Common potato scab and measures to combat the pathogen.

10. Potato macrosporosis and measures to combat the pathogen.