Potato ring rot: pathogen, forms, control measures and prevention

Diseases of vegetable crops, in general, are an unpleasant thing, and when there are no special pesticides to combat diseases, this does not add optimism to most gardeners. Nevertheless, one can and should learn to cope with bacterial diseases of potatoes, since they are widespread and can destroy up to half or more of the annual harvest.

Potato ring rot is one of the bacterial diseases and is found everywhere in all areas where potatoes are grown. The disease is insidious, since its symptoms develop rather slowly and are not immediately noticeable from the outside, although crop losses can be up to 40-45%. In this article you can find photos of signs of the disease, as well as its description and treatment methods. You just need to immediately understand that in the case of ring rot, treatment as such is usually not carried out. Infected plants must be immediately destroyed - they cannot be saved. But disease prevention plays a very important role.

Nature of the disease

The causative agent of potato ring rot is the bacterium Corynebacterium sepedonicum. It does not live in the soil - soil microflora displaces the infection from the site. But tubers are an excellent place for reproduction and wintering.

Under certain conditions, bacteria begin to migrate from mother potatoes to the tops. By filling the vessels of the stems, the pathogen provokes their blockage. As a result, the leaves do not receive enough moisture and wither. Decay is accelerated by toxins released during the life of pathogens.

The disease develops in any weather conditions. At moderate temperatures and a humid climate, wilting occurs more slowly than in the hot, dry season.

Wet rot of potatoes

Wet bacterial rot differs from previous diseases in that the vegetable is susceptible to it much more often during storage, rather than during growth and harvesting. The bacteria that cause such rot penetrate into tissues through external damage caused mechanically or by fungal irritants. During the growing season, the disease develops only in conditions of high humidity and if the soil is already infected with some kind of infectious bacterial disease.

After digging, the cause may be freezing or overheating of the dug potatoes in the sun. Since the disease is caused not by one type of bacteria, but by several, mixed rot has become very common, when fungi of several families interact. As for the symptoms of diseases, wet, soft spots may appear on the surface of the tuber, or there may be no external signs at all. The process of decay begins under the skin: a sharp unpleasant odor becomes noticeable, the affected part becomes pink or dark brown. The place where the healthy part borders on the affected one is separated by a clear brown border. Gradually, the structure collapses and the potato becomes soft; under the skin it looks like liquid gruel or mucus. With the development of wet rot, a liquid emitting an unpleasant odor is released from the surface of the tuber, which infects nearby potatoes. There may be several outbreaks of this kind at the storage location.

Prevention and control of wet rot:

Disease-resistant varieties are selected.
They try to harvest on dry days with sunny weather to avoid dampness. Peel the potatoes from adhering soil and grass residues.
When digging, try not to cause mechanical damage to the tubers, and dry them before placing them in storage.
The storage itself also needs to be carefully prepared. The room is treated with lime or copper sulfate, ventilation is provided, and the temperature regime is maintained. It is believed that ⃝the likelihood of wet rot increasing if the temperature in the basement is above +5C.

Important! If a source of disease is detected, there is no need to sort through the entire volume; simply remove all potatoes within a radius of 20 cm from the epicenter of infection. Then it is sorted, undamaged tubers are suitable for use.

Form and signs of damage

It is difficult to notice the presence of aerobic bacteria that have settled in tubers or stolons. If infected potatoes were planted in the soil, the disease can only be known by the condition of the above-ground parts.

Not the entire bush withers, but only a couple of stems, which very quickly fall to the ground. This is already a clear sign that rot has settled in the tuber (with other diseases, the affected tops remain in a standing position). The tips of the leaves acquire a brown tint, and the plates themselves become covered with white spots due to a lack of chlorophyll.

The signs of the disease can be presented step by step as follows:

the top of the affected stem turns yellow and the leaves on it curl;
the plates look mottled due to the fawn color that appears between the veins;
the lower leaves on the bush wither, become thinner, their edges curl upward;
the tops slow down the growth process and take on a dwarf appearance due to shortened internodes.

A characteristic sign of ring rot is a mucous mass of a yellow-fawn hue that fills the diseased stem. If a cut branch is placed in water, this substance will begin to flow out of it.

In the initial stage of the disease, potato tubers are no different from healthy ones. Therefore, signs of damage do not appear immediately. They can only be detected by cutting the fruit transversely. If infection is present, the vascular ring becomes yellowish and the potato tissue becomes soft.

General information about the disease

The disease occurs in any climatic zones where people grow “second bread”. It occurs due to infection of plants by pathogenic bacteria.

This is an insidious disease because its first external signs appear only at the height of the disease. That is why it is not possible to cure potatoes from ring rot. Affected bushes have to be uprooted and burned. The soil under them needs to be disinfected.

It is possible to prevent the disease. For this purpose, effective recommendations have long been developed. If you know the description of the onset of the disease, then the treatment will be effective.

Specialized means to destroy infection

The action of no chemicals can completely destroy a ring rot infection if the infection has already begun. But slowing down the development of potato disease (or better yet, preventing it) is quite possible. Specialized drugs will help with this:

mineral fertilizers containing nitrogen and potassium, applied during certain periods of crop development, help increase the immunity of potatoes against any bacterial infections;
to reduce the spread of the disease in the area, they control insect pests (before and after flowering of the bushes); fields are treated with complex insecticides such as Shar Pei, Tanrek, Sirocco, Borey Neo;
when sending potato seed fruits for storage, they should be treated with fungicides Quadris and Maxim; the biological product Gamair is also suitable;
Before planting, it is recommended to treat the tubers with TMTD, using 2.5 liters of the substance per ton of potatoes.

In the latter option, precautions must be taken - the product is toxic. But it has a complex spectrum of effects - potato tubers receive protection not only from bacterial, but also other diseases.

Is it possible to eat affected potatoes?

Tubers in which the disease has just begun to develop are not dangerous to humans and are quite suitable for consumption. In such potatoes, the dark ring under the skin is not yet clearly visible and the flesh has not lost its taste.

Potatoes with strong signs of damage , a pronounced unpleasant odor and soft, slimy pulp can no longer be eaten.

Popular measures of struggle

Farmers do not have recipes for using improvised means to destroy the causative agent of the disease. The main measures to combat potato ring rot are as follows:

compliance with crop rotation rules;
use of green manure;
drying the tubers.

To avoid potato damage by any disease, you should not plant the crop in one place year after year. But if this is not feasible due to limited space, then green manure will take on the bulk of the bacteria.

For this purpose, crops with a short development period are selected so that they have time to build up green mass before frost. It is best to immediately sow cereals (spike beans and corn), cabbage, legumes or tobacco on the site after harvesting potatoes.

Potato diseases and measures to combat them

The development of diseases in potatoes is caused by tiny organisms invisible to the naked eye - fungi and bacteria, as well as viruses.

If nothing is done, the disease will get worse from year to year, and the potatoes on the plot may be completely contaminated, unable to produce a full harvest.

Let's look at the main signs of the most common diseases and methods for preventing their spread.

Ring rot

It has been established that the infection can remain for a long time in potato stems and tubers in a hidden (latent) form. The bacterium usually overwinters in affected tubers and does not survive in the soil, but can persist for several years as dried mucus on the surface of containers. With good snow cover and mild winters, it can survive in plant debris.

The development of the disease is slow. The first symptoms are observed in the second half of the growing season of the crop (just after flowering). Moving from the affected mother tuber to the potato stems, the bacteria cause blockage of blood vessels, as a result of which the access of water to the upper part is limited and the stem withers.

In sick plants, individual stems first wither, which soon lie to the ground, then the entire bush withers. Unlike blackleg, diseased stems remain firmly in the ground. The leaves of the affected part turn white, losing chlorophyll. If a cut of a diseased stem is placed in water, a milky mucus comes out of it.

On tubers, the disease manifests itself in the form of ring and pit rot. Ring rot develops strongly in autumn. A section of the tuber along its periphery shows an area of decayed vascular system.

When pressure is applied, a light yellow mass of bacteria and decomposed tissue emerges from the affected area. Rotting spreads to the core and the tubers are completely destroyed.

Affected ones persist to a lesser extent, producing diseased plants when planted.

Pit rot

Pit rot develops in storage in the spring, starting at the end of March, and infection occurs the previous fall during potato harvesting when healthy tubers come into contact with those rotten from ring rot.

This form is revealed only when peeling the peel, under which small rotted pits are clearly visible. The disease is easily transmitted by cutting tubers. By the way, the pitted shape can appear with excessive moisture.

Blackleg and soft (wet) rot

The primary source of the disease is affected tubers and the remains of diseased plants in the soil. The disease is easily transmitted when cutting tubers and through ground or surface water. In rainy years and in low places it occurs in significant sizes.

Caused by two subspecies of Erwinia. The first strain is more active at temperatures below 18°C and causes the black ink symptom (blackleg), while the second strain is more active at temperatures above 18°C and causes stem rot without the black ink symptom.

The bacterium multiplies in the conducting tissues of potatoes, causing characteristic symptoms that appear shortly after field germination of potatoes. Sick plants or individual stems wither, grow stunted, and leaves become smaller. The leaf lobes curl along the central vein with the edges upward, wither and darken. The lower part of the stem rots and turns black.

Bushes and individual stems are easily pulled out of the soil. The tubers are rotting. Brown rot begins from the stolon and gradually affects all parts of the tuber. Affected tuber tissues look like colored, odorless soft rot with a soft, slightly granular consistency.

The area of decay is separated from healthy tissue by a dark brown and black line.

Common scab

Distributed everywhere, it affects potatoes especially severely on light sandy and sandy loam, as well as heavily calcareous soils and is caused by various types of radiant fungi.

Common scab affects tubers and manifests itself in different ways: as rusty-brown scab-like cankers, raised scabs or warts, cankers pressed up to 0.5 cm into the flesh with a reddish or purple bottom, shallow grooves that intersect and resemble a net. Warts or cankers often coalesce, covering the entire tuber with scabs. A white cobwebby coating of mycelium is noticeable on freshly dug tubers. When the tubers dry out, the coating quickly dries and disappears.

The harm from the disease consists of a decrease in the marketable value of tubers: deterioration in taste (starch content decreases by 5-30%), an increase in waste of food potatoes, and a decrease in the keeping quality of tubers.

Infection occurs mainly through lentils or wounds. The disease infection persists mainly in the soil on plant debris after harvesting and partly on planting material. The development of the disease is facilitated by the use of unrotted manure, feces and lime for fertilizer.

Potato blight

Leaves, stems, and tubers are affected. The first signs of the disease are observed on the leaves, starting from the lower ones, and rapidly increasing dark brown spots appear in certain areas of the stem. The leaves turn black and dry out.

The tubers show sharply defined grayish and then brown depressed hard spots of various sizes. On a section of the tuber, under the spot, rusty-colored pulp is visible, spreading inside the tuber in the form of tongues or wedges.

Tubers become infected either during heavy rains, when the infection from the leaves enters the soil, or during harvesting, when the tubers come into contact with the surface layer of soil and with the affected tops. The pathogen penetrates through eyes, lentils and mechanical damage to tubers. Elevated temperatures in storage contribute to the rapid development of rot

Protective measures

Change planting material.
For any operations with tubers - separating and cutting sprouts, cutting tubers - treat the knife with disinfectant solutions.
Maintaining crop rotation and growing resistant varieties.
Warming up the seed material for 2-3 weeks at a temperature of 14-18 °C before storage or at the end of the storage period helps to identify diseased tubers and allows the use of only healthy planting material.
Timely mowing and removal of tops reduces the risk of tuber infection.
Sowing green manure.
Do not apply fresh, unrotted manure, feces or lime under the potatoes.

Source: https://6cotok.org/519291792271870294/bolezni-kartofelya-i-mery-borby-s-nimi/

Prevention

Since root rot cannot be destroyed in the beds, the main efforts are directed towards preventive actions. Only a set of measures can prevent the development of the disease.

For planting, varieties that are more resistant to rot are selected (Voltman, Korenevo, Peredovik). In this regard, early ripening potatoes have weak immunity.
Only beautiful, firm tubers without any damage should be planted. The fruits are sent to the ground whole, without cutting, so as not to provoke infection.
Having discovered a diseased bush on the site, it is completely dug up and, together with a lump of earth, taken away from the site.
In dry weather, do not forget to water the potato bushes.
To maintain plant immunity, fertilize in a timely manner.
A week and a half before harvesting the potatoes, the tops are mowed and removed from the garden.
All equipment used when planting and harvesting potatoes is disinfected with formaldehyde or washed with soapy water and wiped dry.
It is mandatory to treat the storage - walls, floors, racks, drawers. Wooden structures should be replaced with metal ones.
It is not allowed to store planting potatoes together with tubers intended for food.

If you carefully examine the seed potatoes, as well as the tops that have sprung up in the garden, and take timely measures to combat ring rot, this will save most of the crop from infection. Compliance with the rules of agricultural technology and disinfection of the soil after harvesting contribute to the protection of potatoes.

Potato dry rot

Dry rot is one of the most dangerous diseases for potatoes, which spreads very quickly. Its source is a fungus that is found in the soil and affects still young tubers. When transported to the basement, the spores are transferred along with the remains of the soil and continue to multiply intensively during winter storage. The most common disease is dry rot on potatoes: methods of control and prevention will be discussed in more detail.

Favorable conditions for the propagation of furadia blight are considered to be a high nitrogen content in the soil and abundant fertilizing with manure. If the ground is infected with spores, during flowering the first signs of the disease appear, the upper leaves of the green tops begin to lighten, then the stem changes color and the tops gradually fade.

After harvesting, healthy tubers are affected by rot already in the basement. First, gray-brown spots appear on the potatoes; as the infection penetrates deeper, depressions form in place of the spots. The affected areas dry out and become like dust, and voids form inside the tubers, with white fungus on the walls. As a result, the tuber becomes dry, light and hard. Dry furious rot passes from diseased potatoes to healthy ones, so foci of infection form around rotten potatoes. By mid-winter the disease reaches its maximum development.

If you plant potatoes collected from an infected area next year, a new round of the disease cannot be avoided.

Dry rot of potatoes - how to fight:

Only healthy potatoes should be planted. Before planting, you should carefully sort out the tubers, and if there were multiple cases of dry rot in the previous harvest, replace the planting potatoes with purchased ones.
The infection cannot be treated with chemicals. Experienced gardeners advise treating with antibacterial agents. Before planting, you can treat seed potatoes with the following preparations: Fitosporin-M - 500 g/t, Baktofit - 4 kg/t, copper sulfate - 1-2 g per 10 liters of water.
Treatment is carried out not only before planting, but also before winter storage; for this purpose, the drug Maxim KS is used - 0.2 l/t.
How to treat potatoes for dry rot? Preventive measures include light-hardening before lowering the potatoes into the basement. It is dried and laid out for 10-15 days under diffused light, then it becomes more resistant to diseases, is well stored and actively germinates in the spring. But this only applies to the seed batch, because after treatment with light, it is no longer suitable for food.
When planting in spring, to prevent disease, the soil is fertilized with potassium rather than nitrogen fertilizers. The area is cleared of weeds, diseased bushes and unnecessary tops. You can try planting disease-resistant varieties. Do not forget that potatoes cannot be grown in one place for more than 4 years, then the area is changed. If the soil is infected, it is treated with phytosporin and green manure is sown. In a couple of years, they will clear the soil of fungus and saturate it with useful substances.