ᐉ Black leg of potatoes: causes, prevention and control measures

How to deal with black leg on potatoes: control measures and prevention

Blackleg on potatoes is a disease that is caused by soil parasitic fungi or bacteria. Any of the varieties can be susceptible to it, although certain types of nightshades have good immunity. Those who grow crops must know what measures need to be taken in the event of a disease, otherwise the work invested will be in vain. A distinctive feature of the disease is general inhibition of the plant. A photo of a black leg on a potato shows what the disease looks like.

Potato ring rot

The bacterial infection affects all parts of the potato plant. The external manifestation of the disease during the growing season, like the black leg, is withering of the aerial part and rotting of the mother tuber.

Ring rot of potatoes.

A distinctive feature is a leaf mosaic in pale yellow tones and swelling of leaf nodes. 1-2 weak stems develop from the mother tuber. On diseased tubers during harvesting, pitting rot is visible; when cut, the diseased tuber tissue has an annular lesion of the vascular tissue or yellow subcutaneous spotting.

Causes

As a result of potato infection with black leg, you can lose 50% of the entire crop. Previously, it was believed that the disease was caused by 3 closely related bacteria. Now they have been combined into one type. The infected crop looks as if it is in the soil on a thinned black stalk. For some time you may not see negative changes in the development of the plant. From a distance, it seems that the stem has turned black due to being stained with soil. This disease occurs everywhere.

One of the causes of blackleg may be soil contaminated during previous plantings. Sometimes it is not possible to thoroughly clear the area of the crops planted last year. Pathogenic microorganisms do not live in soil. However, they thrive in the smallest grains of organic matter that remain in the soil.

Potatoes can become infected during the preparatory period. Wrinkled and rotten tubers are not suitable for planting, while green ones have the necessary properties and can be planted. It is advisable to divide the tuber in half; on the outside it looks completely healthy, but on the inside it is spoiled. After each potato, the knife must be disinfected. If proper attention is not paid to the autumn harvesting of vegetables, harmful bacteria will develop in the unrotted residues.

The reason for the appearance of black legs in potatoes can be improper storage and transportation. In the cellar, the temperature should be 0°C, the humidity level should be from 50% to 60%. Dangerous bacteria can be carried by various living creatures:

Symptoms of the disease

The fact that potatoes are infected can be judged by yellowing and falling leaves. Sick bushes develop poorly. After the defeat, the stem turns black, then the roots and tubers begin to rot. A sharp, unpleasant odor emanates from the place where the trunk connects to the fruit. The affected parts come off easily.

You can tell if a potato has blackleg if:

in rainy times, after flowering ends, the stem becomes dark green;
as a result of pressure, one feels that there is nothing inside;
At first, brown spots appear on the root crop, and then it darkens and rots.

Alternaria blight (potato dry spot)

In terms of the level of damage to potato yields, this disease is similar to late blight. It affects all parts of the plant (stems, leaves, tubers). Most often, dry spotting affects mid and late potato varieties, that is, those recommended for winter storage.

Alternaria blight (dry spotting of potatoes).

During the growing season, the lesion appears on leaves and stems in the form of large concentric spots. The spots gradually become brown or dark brown with a brown tint. Depressed spots appear on the surface of the tubers, which gradually wrinkle. On a section of the tuber, the affected areas are necrotic and differ from healthy tissue by hard, dense black-brown pulp.

Diagnosis of infection

In most cases, the disease can be identified only after the potatoes have sprouted. Just by examining it, you can see the changes that have occurred. As for the leaves, they are:

lose melatonin;
turn yellow;
curl up;
dry out.

Dangerous microorganisms attack the stems. They turn yellow and wither after a while. The bacteria then spread into the tubers. Gradually everything turns into a soft, rotting and foul-smelling mass. The appearance of diseased potato fruits becomes dark in color. A foul-smelling liquid flows from the cracks that appear, and a void forms inside. In hot weather and high humidity, the disease develops quite rapidly; everything can happen in 4-6 days.

Potato brown rot

Mucous bacteriosis is one of the most severe bacterial diseases. It is distinguished by the rapid course of the disease. It affects about 200 plant species, including potatoes.

Distributed mainly in regions with warm climates. The source of infection is diseased tubers and soil, weeds, and irrigation water. The causative agent of the disease penetrates the tubers of the new crop through mechanical damage, stomata, and fills the vessels of the stems, stolons, and roots with a mucous mass, which causes wilting and death of the plant.

Brown rot of potatoes.

Symptoms of the disease appear externally during the flowering phase in the form of wilting leaves at the ends of the shoots. Green leaf blades acquire a brownish tint, curl into a half-tube and hang. The root part of the stems softens. The bacterial mucus accumulated inside (in the vascular ring) is released through breaks in half-rotten stolons, stems, and rotten tubers.

Control measures

Over many years of practice, experienced gardeners have developed preventive measures and effective methods of treating this type of potato disease. They do not recommend planting the crop in one place every year. If an infection is noticed in growing bushes, they must be immediately removed and burned so that nothing remains of them: neither tops nor tubers. The soil in which they grew must:

loosen;
dry;
treat with copper sulfate and wood ash.

The treatment solution is prepared as follows: 1 tsp. vitriol is mixed with 1 kg of ash. You can bury the ash to a depth of 10-15 cm or spill Bordeaux mixture on the infected area.

No varieties have yet been developed that are 100% resistant to blackleg. But there are still varieties of potatoes that are less susceptible to this disease:

pink Ukrainian;
Spark;
Vilia;
Gatchinsky;
Volzhanin and others.

Biological remedies

These include strict adherence to the rules for storing crops. The room must be treated and maintained at a suitable temperature and humidity. Plant more resistant varieties in well-dried soil, on which there should be no remaining tops or unharvested rotten tubers.

Related article: Is it possible to eat sprouted potatoes and what else to do with them

It is forbidden to prepare compost by adding diseased plants to it. To prevent the appearance of bacteria and neutralize soil acidity, it is recommended to use dolomite flour. The grown crop must be carefully sorted, and then do not forget to leave it to dry.

Chemicals

If the above control methods do not give a positive result, treatment is carried out with chemicals. It is recommended to treat potatoes intended for planting:

1% solution of Bordeaux mixture;
"Fitosporin-M";
TMTD.

10-15 drops of “Fitosporin-M” are dissolved in 1 liter of water. The solution is prepared for preventive purposes for the treatment of tubers. If it is to be used for treatment, you will need 10 ml of the drug and 10 liters of water. The “Hom” product helps fight black leg in potatoes. To spray the bushes, 4 g of the drug is diluted in 1 liter of water. Before hilling the bushes for the first time, experts advise spraying them with Energen. To prepare a working solution, 5 ml are diluted in 10 liters of water.

To disinfect the soil, it is watered with a solution of potassium permanganate, as well as one of the following chemicals:

Treat with a composition prepared from 2 g of one of the drugs mixed with 1 liter of water. For prevention purposes, you can use “Effecton”: 3 tbsp. diluted in 10 liters of warm water, irrigate the bushes and soil. Experts advise that before storing potatoes, treat them with Maxim.

Lyudmila. Oryol Region:

When growing potatoes, I sometimes notice that they are infected with blackleg. I’m trying to prevent the infection from spreading throughout the entire area; I treat the soil with Topsin-M. It is a chemical product, so I follow the proportions exactly. I'm quite satisfied with the result.

Alexander. Perm:

I plant potatoes at the dacha. Before planting, I treat the tubers with TMTD. I believe that thanks to him I have been able to dig up a large harvest for many years.

Catherine. Krasnodar region:

When a neighbor showed me blackened potatoes, I began to be very careful about planting tubers and sorting them out more carefully. I definitely treat it with Fitosporin-M, and the result is an excellent harvest.

Black leg on potatoes is a progressive disease. In order not to lose the entire harvest, experienced gardeners recommend paying attention to preventive measures. Finding and testing methods for dealing with black leg on potatoes is much more difficult than preventing its appearance. If agrotechnical procedures are carried out correctly, it will be possible to cope with the disease effectively and in the shortest possible time. The quality of planting material and compliance with crop rotation are of great importance.

What is a black leg?

Previously, it was generally accepted that blackleg disease was caused by three types of bacteria. Now scientists have brought them together into one single group. The bacterium is a short rod with rounded edges and can form short chains. It does not form spores or capsules and is an anaerobic species.

A sign that potatoes are infected with blackleg is darkening of the base of the stems. If there is at least one diseased tuber in the storage, then before spring it will infect many more potatoes . The pathogen cannot overwinter in open ground, since it necessarily needs a nutrient medium, which is not only the tubers themselves, but also the remains of vegetation and tops.

Potato rot: why do potatoes rot during storage, and how to avoid it?

Despite the fact that potatoes are on sale in the markets all year round, you want your own - incredibly tasty, boiled and environmentally friendly potatoes. But often home-grown potatoes cannot be preserved until spring. After the New Year holidays, increased “spoilage” of tubers begins, an unpleasant odor appears in the storage facility and even (as they write in the newspapers) an explosive situation when gas accumulates in a closed room. What causes tuber rotting, and how to avoid it? Let's understand the reasons and develop a scheme for preserving the harvest of our favorite potatoes.

Why do potatoes rot during storage and how to avoid it.

Causes of the disease

The cause and development of blackleg are rod-shaped bacteria, which in a favorable environment multiply very quickly and unite into colonies. The disease spreads across many cultures, so there is no nutritional deficiency for the virus.

The development of the disease is provoked by the presence of pathogens on the site that can successfully overwinter in the remains of vegetation. Also, gardeners often purchase infected potatoes for planting, which by the time of harvesting were already carriers of the infection. Violation of the rules of transportation and storage, insect carriers and lack of nutrients in the soil are also favorable factors for the development of blackleg.

Symptoms of the disease

Signs that potatoes are affected by blackleg are:

yellowing and falling leaves;
the stem and root turn black, at the site of the lesion they are easily torn off;
developmental lag of diseased bushes;
with severe damage, the disease spreads from the stem to the root and tubers;
the junction with the root crop rots and has a strong unpleasant odor;
in the rainy season, after flowering, the potato stem becomes dark green in color, and when you press on it, you feel empty;
Initially, the fruit becomes covered with brown spots, after which its tissues darken and rot.

Late blight of potatoes

Late blight is one of the most dangerous fungal diseases. The fungus infects the crop during the growing season (it can destroy up to 70% of the crop in a short period) and is transported with the tubers to storage areas.

Late blight of potato tubers.

Hard gray spots appear on the surface of the tubers, clearly visible on the pulp when cutting the potato. With the growth of the mycelium, the tuber begins to rot.

Diagnosis of infection

The bacteria that cause the development of blackleg spread from the stem to the tubers, turning them into a rotting mass that emits an unpleasant aroma. The color of diseased potatoes varies from light to dark.

A characteristic viscous liquid with a strong unpleasant odor flows out of the cracks of the affected tubers, and a void forms inside them.

Externally, diseased potatoes are distinguished by the presence of cracks and dark skin. As a rule, it is possible to diagnose blackleg only after germination. The foliage immediately turns yellow and falls off, the stem also turns yellow and dries out over time. Under its own weight, the stem can break, and at the point of break, signs of rotting are clearly visible. The potatoes themselves are easily pulled out of the ground.

Related article: Azofoska for potatoes: instructions and fertilizer rates

Signs of illness

From the affected soil, the fungus along with nutrients enters the plant stems. The tips of the leaves begin to turn pale and turn whitish. A pink coating appears on the stem. The mycelium grows and completely covers the stem, preventing further penetration of nutrients and moisture into the leaves. Deprived of nutrition, the growth of the bush slows down, the leaves and tops quickly wither and dry out.

During winter storage, 1-2 months after harvest, brown spots begin to appear on the tubers. Over time, the spots increase in size and become sunken. The affected areas dry out and become like dust, and voids form inside the tubers, with white fungus on the walls. Over time, the tuber turns into a hard and light ball.

Treatment methods

Over the years of practice, gardeners have developed not only preventive measures, but also effective methods of treating blackleg:

You cannot plant potatoes in the same place for several years in a row.
If potato bushes with black leg are found in the plantings, then it is necessary to immediately loosen the soil, dry it, add wood ash or dust from charcoal.
In cases where other methods are ineffective, they resort to the use of chemicals (for example, “Energen”, 5 ml of which is diluted in 10 liters of water and the resulting solution is poured over potatoes).
In the fight against blackleg, the drug “Hom” has proven itself well, 4 g of which should be diluted in 1 liter of clean water and sprayed on the bushes.
Diseased potato bushes are removed from the site along with the tops and tubers, and the soil where they grow is treated with a solution of wood ash and copper sulfate.
Before the first hilling, the plants are sprayed with Energen solution in a proportion of 10 ml per 10 liters of water.
The tops from infected bushes are burned, and the tubers are sorted and tried not to be stored together with healthy material.
Before planting, potatoes should be disinfected by spraying with a 1% solution of Bordeaux mixture.
When growing seed potatoes, the bushes are cleaned three times: after emergence, during flowering and before harvesting.

Reviews

Vladislav, 42 years old
We have been growing potatoes for many years. Very rarely in our area we come across bushes that suffer from blackleg. We try to constantly monitor the bushes. We immediately destroy all suspicious plants. It is safer to sacrifice one bush than to later lose most of the harvest. The disease spreads quickly and has almost no cure. Be sure to treat the tubers before planting.

Marina, 36 years old
I advise everyone to treat seed potatoes with Fitosporn-M before planting. I always buy it to protect potatoes from blackleg. This treatment gives good results. In combination with proper care, it is guaranteed to protect against the occurrence of disease.
Read also: How to properly dry onions after harvesting from the garden and at home for the winter

Blackleg is very dangerous for potato plantings. The bacteria that cause the disease spread quickly. Preventative measures are effective in combating the disease. Therefore, before planting, potatoes must be treated with special preparations and care rules must be followed.

Preventive protective measures

If blackleg disease is not detected in the area, but there is a danger of its occurrence due to favorable conditions for the growth of bacteria, then it is recommended to immediately begin preventive measures.

Biological agents

Biological methods of protecting potatoes from blackleg are considered the safest and do not harm the human body or the environment. These include:

Compliance with the recommended rules for storing crops, carrying out treatments in storage, maintaining temperature and humidity at the proper level.
Growing potato varieties with high resistance to blackleg (for example, Vilia, Carnea, Ulyanovsky, Skorospelka 1).
Drying the soil on the site, timely removal and burning of vegetation residues.
You cannot use diseased tops or other vegetation as compost; they must be burned and the ash must be buried to a depth of at least 15 cm.
Use dolomite flour on the site to reduce acidity and prevent the massive proliferation of bacteria.
The harvested potato crop should be carefully sorted and dried.
Tubers that have mechanical damage are subject to rejection and are not allowed to be planted, since this is the material that is most susceptible to disease.

Chemicals

If the risk of potato being affected by blackleg is very high or signs of the disease have been noticed in the area, then you will have to resort to the use of chemical preparations. Reviews from gardeners indicate that the greatest effectiveness is achieved by:

Spraying potato tubers before planting with products.
The area where it is planned to plant potatoes is watered not only with a weak solution of potassium permanganate, but also with preparations designed to combat fusarium (for example, Previkur, Fundazol, Topsin-M and others).
A preventive measure is watering with the addition of Effekton, which is diluted in a ratio of 3 tbsp. l. for 10 liters of water. 0.5 liters of solution is added to each potato bush.
Before being sent to storage, potato tubers are treated with Maxim.

Timely preventive measures will help protect and preserve the potato crop and prevent the appearance of such a dangerous disease as black leg in the garden plot.

Danger of pathology

The pathology of Erwinia carotovora manifests itself in several forms - damage to tubers, infection through foliage and stems, infection of plant residues during composting and mulching.

Potatoes affected by blackleg are usually affected by several other bacterial diseases, and this is the main danger of the pathology of the disease.

Another equally dangerous factor of the disease is its adaptability to various conditions. Under normal conditions, infection is carried out not by one, but by several species. So, under normal conditions, blackleg cannot overwinter in the ground; this requires a nutrient medium for the proliferation of bacteria. In addition, you need to understand that a prerequisite must be suitable temperature and humidity. For bacteria, the favorable moment for the start of reproduction is air temperature above +2 degrees. And the disease reaches its maximum spread at a temperature of +15-18 degrees.

If we take into account that such a temperature regime and the corresponding humidity are maintained in vegetable stores, then in winter the infection not only does not stop, on the contrary, it continues, and in very favorable conditions.

How can you tell if a plant is infected?

Observing the appearance of the plant will help to timely identify the disease in potatoes and take measures to destroy it. A characteristic sign of the disease is the presence of blackened stem bases approximately 10 cm upward. Hence the name.

The main symptoms of the disease:

The first sign is yellowing of the leaves, curling and drying. They are detected 3–4 weeks after germination.
The stems and roots of the plant begin to turn black. And they easily come off at the site of injury.
When flowering, diseased bushes lag behind others in terms of development. The active development of the disease occurs precisely during this period.
If the disease is in an advanced stage, then the bacteria move from the stem to the tubers.
The junctions of stolons with root crops become rotten and emit an unpleasant odor.
In rainy summers, the stem of a faded plant begins to deteriorate and the color becomes dark green. If you squeeze it, there is a feeling of emptiness in this place.
The bulb can become infected from the soil or from a nearby infected fruit. First, the potatoes become covered with brown spots, then the tuber tissue turns black and begins to rot.
If conditions are unfavorable for the development of the disease, it still develops, but in a slow form. It will only begin to progress next year.

Related article: How to make a potato drip irrigation system with your own hands

A careful inspection of potato bushes will help to identify diseases in time and take the necessary preventive measures. After all, those bushes that are affected by the black leg do not form tubers.

What conditions does the virus need for favorable development?

No disease will begin to actively develop if the environment resists it. Conditions that bacteria need for their active reproduction and progression:

Presence of virus in soil. The presence of remains of affected plants in it.
Planting infected seed.
Potatoes were damaged during harvesting.
The conditions for proper transportation and preservation of the vegetable were not met.
The disease is transmitted by insect pests.
Lack of nutrients in the soil.

The disease progresses best in rainy weather and damp summers.

Breeders have not developed a potato variety that is resistant to blackleg. But there are species that are more resistant to this disease.

What is the causative agent of the disease?

These are a kind of bacteria that are rod-shaped. If the conditions suit them, they reproduce very quickly. Uniting in colonies, they begin to infect plants. Many cultures are susceptible to this disease, so it does not experience a lack of nutrition.

The bacterium cannot overwinter in the soil on its own, so it looks for plant remains and tubers. Will survive the winter in the stem or root part of the weed. With the onset of warmth, it continues to reproduce. That is why it is recommended to remove all plant residues from fields.

How to deal with black leg on potatoes?

There are measures to combat the disease that have been proven over the years. It develops very quickly and persists on all plant debris. Effective methods of treatment are competent prevention:

Quality seeds. It is advisable to plant tubers that have sanitary documents confirming compliance with quality standards.
Uncontaminated soil. Be sure to carry out crop rotation. If the site is already infested, it is better to refrain from growing potatoes on it for the next 3-4 years.
Favorable soil. The best environment for the development of the disease is damp clay soil. The acid contained in its composition can be neutralized by dolomite flour. It also destroys bacteria.
Feeding. Microorganisms cannot tolerate sulfur. If the lower part of the plant turns black, it means that infection has begun. You can treat them with ammonium sulfate.
The drug "Effekton". Take 3 tbsp. spoons per 10 liters of warm water, treatment is carried out before the first hilling.

Removing infected bushes. After discovering the source of the disease, the affected plants are pulled out and burned or buried to a depth of at least 1 m, sprinkled with bleach. The bushes need to be removed several more times until the flowering period ends. The place where the diseased plants grew is sprinkled with a mixture of wood ash (a liter jar) and copper sulfate (1 teaspoon).
Prevention before harvest. About a week before digging, the tops should be mowed. Parts of the plant affected by rot are burned in areas that do not belong to agricultural crops.
Collect only on dry days. Be sure to remove adhering soil particles. If tubers from an infected bush seem healthy in appearance, it is better to remove them separately. Being next to a healthy root crop, they can infect it. And so along the chain the disease will spread through healthy vegetables.
Prevention before storage. Drying of the harvested crop is carried out in the sun, or in specially designated places. The seed material can even be slightly greened.
Drug "Maxim". They spray potatoes with it before storing them. 100 ml of the drug per 1 liter of water.

Drying the premises. Several months before harvesting potatoes for storage, all warehouses and cellars are ventilated. And they are treated with disinfectants, lime and vitriol.
Equipping rooms with ventilation and creating optimal temperature. The ventilation is mechanical, and the temperature is approximately +1–3 ⁰С.
Prevention of disease after flowering. To slow down the rate of development of the disease, you can sprinkle the infected bushes with ash or treat them with a solution of potassium permanganate (3 g per 10 liters of water).
Processing of planting material. This is done in the fall or directly in the spring. Special preparations are purchased, phytosporin consumption, bactofit and others.
Disinfection of instruments, provided that the seed is cut. To prevent bacteria from spreading to healthy tubers, it is recommended to dip the knife in a solution of potassium permanganate.

A preventive measure is the destruction of insect pests, they are carriers of the disease.

Treatment of plants must be carried out immediately after detection of the disease. This way you can save neighboring plants from spreading the disease throughout the entire area.

Tips from summer residents

Blackleg disease is very progressive. In order to prevent most of the harvested crop from rotting, summer residents advise paying more attention to disease prevention. Since treatment is a labor-intensive process. The presence of blackening stems indicates the active development of the disease. The following will help prevent development:

Three times weeding. Removing diseased plants at least three times. With subsequent disinfection of germination sites.
Treatment of seed and the site itself with preparations after germination.
Regular inspection of bushes, at least once a week.

It is important to remember that any matter is taken seriously. By following the measures, rules and requirements, you get an excellent harvest. Everything is in the hands of the gardener.

Sources:

https://zelenj.ru/kak-borotsya-s-chernoj-nozhkoj-na-kartofele.html https://moefermerstvo.ru/kartofel/chernaya-nozhka-borba https://dachamechty.ru/kartofel/chernaya- nozhka-borba.html