Wilting of agricultural plants caused by parasitic fungi. Plant diseases caused by fungi. Bacterial. Viral diseases. How is verticillium wilt infected?

Fungal plant diseases are the most widespread diseases of agricultural plants. They account for more than 80% of all plant diseases. There are many ways of infecting plants, for example, fungi can penetrate into plant tissues through stomata, lenticels, through epidermal cells, wounds and cracks from sunburn. In addition, insect pests can be carriers of infection ( ), which greatly facilitate the penetration of fungal infections into the plant. Fungal spores and mycelium elements are perfectly preserved in soil, plant debris, carried by wind, raindrops, etc.

powdery mildew- a very common fungal disease that affects the aerial part of the plant (shoot). First, a white coating appears on the leaves, at the ends of young annual shoots, less often on the inflorescences, which eventually becomes like felt. The plaque is compacted and covered with many black dots (fruiting bodies of the fungus). Affected plants are strongly inhibited, their growth and fruit formation slow down, which, ultimately, can cause death. The spores are well dispersed by the wind. The spread of the disease is favored by high humidity in combination with a comfortable air temperature for development. Also, strong pruning, excess nitrogen in the soil and a number of other factors that negatively affect immunity can contribute to development. All pathogens of this disease (Uncinula necator (Oidium) causes the appearance of powdery mildew on the vine, Sphaerotheca mors - on gooseberries, Erysiphe graminis - on cereals, Sphaerotheca pannosa forma persicae - on peach, Erysiphe communis - on sugar beet, Sphaerotheca pannosa Lew. var. rosae Voron. - on roses, Erysiphe cichoracearum, Sphaerotheca fuliginea - on gourds), tolerate winter well in the soil and on infected plant shoot residues.

Under favorable conditions (high humidity and favorable temperatures), powdery mildew affects almost all crops and flowers. The problem of the spread of powdery mildew is especially acute in greenhouse complexes, where there are all conditions for the spread of infection, especially if the premises are not ventilated.
Prevention and treatment of powdery mildew:

• sparse landings;
• loosening the soil;
• the introduction of increased doses of phosphorus and potash fertilizers;
• Chemicals;

plant rust- a fungal disease that manifests itself on the upper side of the leaves in the form of small yellowish-orange or red-brown, rust-like spots, sometimes slightly raised. Gradually they increase in size. Affected leaves and even whole shoots dry out over time, premature leaf fall begins, the stems in the affected areas can break. Diseased plants weaken, their winter hardiness decreases.
Spores hibernate on fallen leaves or in the soil. Most rust fungi develop on several plants: the causative agent of rust on sakura takes place on juniper, rust on decorative plum on anemone, columnar rust on Siberian cedar and Weymouth pine, and the causative agent of goblet rust overwinters on sedge.

Fungi that cause rust are related sooty mushrooms, which provoke the appearance of a black coating on cereals and champignons (a sooty coating appears on the affected plants). Most often, rusts affect plants growing outdoors, such as roses, bearded carnations, snapdragons, mallows, anemones, and some types of greenery, such as mint. The only effective method of combating this disease is the removal and subsequent destruction of all infected plants and their parts (leaves and stems) and treatment with fungicidal preparations. You also need to remember that moist air favors the spread and development of the disease. In addition, rust often affects plants with weak immunity, or with a deficiency of macro and microelements, in particular potassium. To ensure that the soil always has the required amount of potassium, you need to regularly apply potassium fertilizers to it. Rust inhibits plant growth and causes deformation of its stems and leaves. All affected plants are burned. In case of a weak infestation, the plants can be sprayed with a fungicide. Remember to collect and destroy (better burn) all rust-affected plant leaves that have fallen to the ground. Some types of rust fungi have a very complex life cycle and require two hosts. It is quite difficult to destroy such a fungus, much more difficult than a fungus with a simple development cycle.
Prevention and treatment:

• growing rust-resistant varieties;
• eradication of wild intermediate rust hosts around orchards;
• collection and destruction of fallen leaves.
• Biological fungicides;
• Chemicals.

spotting- a symptom of plant diseases with fungal infections with the formation of dry spots on leaves, stems, flowers, fruits and other parts of plants. The spots are varied in color, size and shape, often bordered by a darker rim, sometimes sporulation of the fungus can be observed on the surface of the spots. Initially, the spots are single, then multiply and increase, merge with each other. The disease causes premature aging of the leaves (in wet weather, autumn color may appear already in July), they dry out and fall off prematurely. The decorativeness and productivity of plants are sharply reduced. Pathogens overwinter on plant debris, so fallen leaves and removed stems should be burned.

White spotting (septoria) in most plants affects the leaves.
Black spot (alternaria) affects leaves and seeds.
Red spot affects cherry blossoms, which can shed flowers.
Ascochitosis begins with the appearance of reddish spots on the leaves and stems.
Brown spots (phyllostictosis, mereniosis), in addition to leaves, affect fruits that remain underdeveloped, acquire an ugly shape, crack, turn brown, crumble; the stems die when ringed with spots.
Anthracnose affects not only leaves (convex or depressed spots, with pads of sporulation of the fungus), but also stems, shoots, berries.
Infectious burn affects the branches of roses under winter shelter when (on the branches, after removing the shelter, there are reddish, later darkening spots, which, growing, ring the shoots, and they die; black sporulation of the fungus appears on the dead bark).
Prevention and treatment:

• the use of disease-resistant varieties;
• crop rotation;
• timely removal of shelters in the spring;
• thinning bushes;
• wound treatment;
• digging the soil;
• destruction of weeds and plant residues;
• the use of biological products;
• chemicals.

Rotten succulent, nutrient-rich and woody parts of plants are susceptible - fleshy leaves, flower buds, flowers, fruits, roots, corms, stems. The development of rot is facilitated by thickened and deep planting, high soil and air humidity, excessive application of nitrogen fertilizers and infected planting material. Plants are covered with yellow and brown spots, lag behind in growth, bloom and bear fruit poorly, rot and often die. The affected areas are covered with a pink, white or brownish coating of the fungus. Often the disease passes to the base of the stems, roots, bulbs and tubers (they die in poorly ventilated stores by spring). Root rots settle on the roots of plants (often at the root collar), causing them to rot and die off. The pathogen lives in the soil. The leaves, starting from the bottom, turn yellow and dry. When the root neck is damaged ( root rot) the base of the stem turns brown, splits into fibers, the skin on it cracks.

Gray rot- one of the most dangerous diseases that affects all above-ground parts of plants, a gray fluffy coating of accumulations of fungal spores appears on them.
Blackleg affects young plants - seedlings, seedlings, cuttings. The disease spreads in high humidity. The tissue of the root neck and the base of the cuttings turns black, the stem becomes thinner. Sick plants lose turgor, turn yellow, droop, lie down and die.

• use of healthy planting material;
• planting cuttings, bulbs and rhizomes to the proper depth;
• liming of acidic soils; application of recommended doses of fertilizers;
• watering as needed;
• compliance with storage rules;
• culling of diseased plants;
• biological products;
• chemicals.

Ulcerative (common) cancer associated with cortical damage. Brown spots appear on the leaves, then they turn brown and fall off. Black rot forms on the fruits, subsequently they become mummified. In places of damage - on the trunk, skeletal branches, especially in the forks - sagging and deep cracks are formed, sometimes reaching the core of the tree. With a strong development of the disease, the trees die within 3-4 years.

Preventive methods of protection:

• protection of the bark and skeletal branches of plants from mechanical damage (including grafting), sunburn and (whitewashing in spring and autumn with a solution of lime with the addition of copper or iron sulfate);
• cleaning and healing of wounds: treatment with a 1-3% solution of copper sulfate or Bordeaux liquid or a 2-5% solution of potassium permanganate;
• collection and destruction of affected fruits and leaves, fallen bark;
• severely affected branches and trees are cut out and burned;
• biological products.

Under the influence of pathogenic fungi, pathological processes occur in plants, accompanied by a violation of the structure and physiological functions of the plant or its individual parts, for example, the formation of growths, influxes, changes in respiration, assimilation, enzymatic activity, impaired growth and development, and death of affected tissues. Outwardly, G. o. R. characterized by one or another type of lesion, which is local or general. Local lesions, covering small areas of the plant or its individual organs, include spotting (cercosporosis (See Cercosporosis) of beets, apple and pear scab, etc.), fungal raids (Powdery mildew etc.), ulcers, pustules (plant rust); to the general - withering of plants.

G. b. R. transmitted by seeds, tubers, bulbs, roots, cuttings, seedlings, and other parts of diseased plants. The infection can persist in post-harvest residues, in the soil, be carried by wind, raindrops, animals and humans, containers, agricultural products. machines and tools. Pathogenic fungi can enter plant tissue through stomata (mildew of grapes), water pores, lenticels, through epidermal cells and cuticles (cabbage club, potato cancer), hail wounds (corn blister smut), sunburn, frostbite (black apple tree cancer), through cracks. Many insects, damaging plants, open the "gates" of infection, while often carrying pathogens.

Chemical measures consist of treatment with fungicides (see. Fungicides) of seeds (see. Dressing), vegetative plants, disinfection of agricultural plants. premises, storage facilities, soil, etc.

Lit.: Naumov N. A., Diseases of agricultural plants, 2nd ed., M. - L., 1952; Natalina O. B., Diseases of berries, M., 1963: Dictionary-reference book of a phytopathologist, ed. P. N. Golovina, 2nd ed., L., 1967: Tupenevich S. M., Shapiro I. D., Protection of vegetable crops and potatoes from diseases and pests, 3rd ed., L., 1968.

S. M. Tupenevich.

Great Soviet Encyclopedia. - M.: Soviet Encyclopedia. 1969-1978 .

See what "Fungal plant diseases" are in other dictionaries:

fungal plant diseases- Table 25. Fungal fruit diseases: 1 - gray fruit rot of stone fruit (plum); 2 - milky shine of an apple tree; 3 - the same, the fruiting of the fungus on the bark of a tree; 4 - apple scab; 5 - apple fruit rot and mummified ... ...

The processes that occur in the plant under the influence of various causes of pathogens and adverse environmental conditions are manifested in the violation of functions (photosynthesis, respiration, synthesis of plastic and growth substances, water flow, ... ...

Plant diseases - processes that occur in a plant under the influence of various causes of pathogens and adverse environmental conditions, manifest themselves in impaired functions (photosynthesis, respiration, synthesis of plastic and growth substances, ... ... Wikipedia

See Plant Diseases... Agricultural dictionary-reference book

QUARANTINE PESTS AND DISEASES- naib, dangerous pests and diseases, which are absent in the country or distributed in part of its territory, but can be listed in decomp. rny country or penetrate independently, spread and cause damage with. X. cultures. The threat… …

Plant pests and diseases of quarantine importance for the USSR (1986)- I. Not registered in the USSR A. Pests of plants 1. Orange scale insect + Unaspis citri 2. White-rimmed beetle Pantomorus leucoloma 3. Large mandarin fly Tetradacus citri 4. Eastern mealybug Pseadococcus citriculus ... ... Agriculture. Big encyclopedic dictionary

agricultural plant diseases- diseases of agricultural plants, pathological processes occurring in plants under the influence of pathogens and adverse environmental conditions; manifest themselves in violation of photosynthesis, respiration and other functions, cause damage ... ... Agriculture. Big encyclopedic dictionary

DISEASES OF AGRICULTURAL PLANTS- patol. processes occurring in plants under the influence of pathogens and adverse environmental conditions; manifested in the violation of photosynthesis, respiration, and other functions, cause lesions of the otd. organs or premature death. B. s. R.… … Agricultural Encyclopedic Dictionary

Diseases characterized by the formation of spots of dead cells on leaves, stems, fruits and other parts of plants; a special case of Necrosis. Causes of occurrence: lack of elements of soil nutrition of plants, pollution ... ... Great Soviet Encyclopedia

Books

• Fungal diseases of strawberries and strawberries. Monograph, Govorova Galina Fedorovna, Govorov Dmitry Nikolaevich. The monograph summarizes domestic and foreign experience, the authors present the results of their own long-term studies of diseases and breeding characteristics of strawberries and strawberries.…

Verticillium wilt is a very serious fungal disease. The fungus that causes this dangerous disease is quite insidious, it can stay in the soil for a long period of time and not cause any harm to plants, but at some point it can suddenly begin to attack the culture, which often leads to the complete death of the plant organism. In this publication, we will consider the main symptoms of plant damage by this disease and methods for the prevention and control of verticillium wilt.

Grapes with signs of verticillium wilt. © syngenta

How is verticillium wilt transmitted?

Verticillium wilt, otherwise called "wilt", is caused by a fungus belonging to the genus Verticillium. Usually plants become infected with this most dangerous fungus through the soil. At the initial stage of its development, the disease negatively affects the young shoots of the plant, which are not able to resist the disease, which is why they usually die first.

Plants that are most severely affected by verticillium wilt have various lesions on the root system or in the lower part of the stem. These damages can be caused by both pests that live in the soil, and the person himself. For example, when digging up a seedling from a nursery or when transplanting a plant to another place, when planting seedlings, improper (excessively deep) tillage, or excessively active work with soil near the trunk.

Interestingly, the fungus that causes verticillium wilt can live in the soil for up to ten, and sometimes more, years, so if the disease has manifested itself, then it is better to keep this area under black fallow for at least a couple of years. In addition, the fungus can live for a long period of time in plant debris, including the remains of plants infected with it, therefore, such plants must be removed from the site and burned outside its territory, preventing plant parts affected by the fungus from entering the soil layer.

After the fungus penetrates the root system or the lower part of the stem, it begins to actively spread along the numerous xylem bundles along with the upward flow of water and dissolved nutrients through the plant. If the soil is infected with this fungus, then even seedlings that have barely appeared on the surface of the soil can die quite quickly, having previously twisted like a spiral.

The fungus develops most actively on soils that are excessively moist (subject to excessive watering of the soil or in areas with close standing groundwater), as well as in years with an excess amount of natural moisture that falls in the form of rain or fog.

Also favorable periods for the development of the fungus are seasons with sharp changes in day and night temperatures. In addition, in neglected areas where plants are affected by pests, the fungus also develops very actively.

As for temperature, the fungus that causes verticillium wilt develops especially actively at temperatures from 16 to 21 degrees above zero. If the temperature drops below 16 degrees Celsius, then the fungus may stop developing, during this period you can notice the formation of new shoots in plants, which, when warmed, can be infected with the fungus quite quickly.

The fungus that causes verticillium wilt is also dangerous because it can attack a wide variety of plants, both vegetable and fruit, berry and ornamental. Quite often, you can notice signs of verticillium wilt on apricots, grapes, tomatoes, roses, chrysanthemums, lilacs, phloxes, strawberries and a whole series of very different plants.

Symptoms of verticillium wilt

The insidiousness of the fungus and the danger of this fungal disease lies not only in the fact that the fungus can be in the soil for a long period of time, both before and after infection of plants, but also in the fact that symptoms of infection, especially on perennial plants, are often observed. one or even two seasons after the infection occurred.

Usually, the presence of verticillium wilt on plants can be noticed only after the shoots begin to die. The death of the shoots does not occur at the same time, while the plant as a whole may look good and even bear fruit, other branches may completely dry out in the same period of time.

Leaf blades on dying shoots first begin to dry out along the edges, marginal necrosis forms, and then the leaves completely dry out and fall off much earlier than the due date. This leads to a disruption in the operation of the photosynthetic apparatus and negatively affects the plant as a whole, including weakening its immunity, reducing winter hardiness (if it is a perennial plant).

Usually, first of all, leaf blades located in the lower tier begin to turn yellow and die off, gradually the disease kills all leaf blades located on the infected branch. If the plant is heavily affected by verticillium wilt, then often only its upper part remains alive.

With a strong infection, drying and falling off of ovaries or fruits in varying degrees of maturity is also observed, which depends on the time of infection and the rate of development of the fungus in the plant.

Sometimes it is possible to determine whether a plant is infected with verticillium wilt by cutting the shoot. On the cut, sometimes a strong darkening of the tissues is noticeable, but, unfortunately, such obvious signs do not always appear.

Fight against verticillium wilt

It can be extremely difficult to cure plants infected with verticillium wilt and exterminate the fungus in the soil. In the event of the onset of very unfavorable conditions for the life of the fungus, it can form sclerotia, form mycelium, even when at rest. With the formation of sclerotia, the fungus can live in the soil for several seasons, even if extremely unfavorable conditions are created for its existence.

Of course, the sooner you identify the disease and the sooner you start to fight it, the higher the chances of getting rid of the plant organism from this disease. Otherwise, the fungus can develop in the soil and spread actively, infecting an increasing number of a wide variety of plants grown on the site.

The first step in the fight against verticillium wilt can be multiple (4-5 times) treatment with copper-containing preparations or fungicides approved for use. In the case of fungicides, it is better to start with biological preparations, such as, for example, Gliocladin, which is an analogue of Trichodermin. It is good because it has a contact and systemic effect, is not addictive to the fungus, restores soil microflora and even removes soil toxicity after the use of other chemicals.

Biological fungicides include "Fitosporin-M, P", this drug can also be used to disinfect seed material, because often the fungus that causes verticillium wilt enters the soil, and then into plants with seeds infected with it.

Of the chemical fungicides, the drug "Maxim, KS" fights well with verticillium wilt, this drug is used to combat fungus in the soil, to disinfect seed material and bulbs of flower plants.

Unfortunately, these drugs and many others do not always cope with verticillium wilt. If no effect is observed, then it is necessary to remove the plant from the site, treat the place where it grew with copper-containing preparations and not plant this type of plant in this area for at least five years.

Wilt prevention

Of course, it is much easier than fighting to prevent the appearance of a fungus that causes verticillium wilt in your area. To do this, you must follow a number of important, but simple rules for growing plants.

The first rule is the observance of crop rotation and crop rotation. So, if we are talking about perennial crops (for example, apricot), then they should be planted in the same place after uprooting the site no earlier than five years later. If we are talking about annual vegetable or flower crops, then they should be planted on the site in three or four years.

After harvesting or at the end of flowering in the case of annual plants, all plant debris must be removed from the site. On perennial tree crops or berry bushes, the entire crop should be harvested completely, diseased and rotten fruits should also be removed from the branches and burned outside the site. In years with high soil and air humidity, characterized by sudden temperature changes, it is also necessary to remove all leaf litter and burn it outside the site.

Another important, but rather simple precautionary measure to implement is to try to prevent the soil from drying out too much on the site. Soil moisture must be maintained constantly at a normal level, that is, it should not be allowed to dry out or be waterlogged, and if there is excessive waterlogging due to heavy rainfall, then it is necessary to loosen the soil more often (every 2-3 days) to allow moisture to evaporate better.

When watering, it is important to use water at room temperature, but it is impossible to water plants with cold and icy water from a hose, contrary to a common misconception, this will not lead to hardening of plants, but can cause stress and reduce their immunity.

Apply enough fertilizer to the soil, do not abuse nitrogen and do not allow plants to become deficient in phosphorus and potassium fertilizers. In order for fertilizers to be assimilated by plants as fully as possible, the soil must be neutral in acidity, but if it is acidic, then dolomite flour or lime must be added to it.

As a prevention of verticillium wilt, it is desirable to treat soil and seeds with natural fungicides, as well as the root system of seedlings when planting. So, infusions and decoctions of tobacco leaves, chamomile plants, as well as infusions of wood ash, soot and charcoal have a fungicidal effect.

In conclusion, about some secrets of experienced gardeners and gardeners. It is noticed that the fungus does not develop or does not appear at all, on sandy, well-drained soils with a neutral reaction of the environment. It has also been recorded that many weeds also suffer from verticillium wilt, so weeds should be controlled and try not to embed their vegetative mass in the soil, especially in areas and in those years when the risk of disease is high.

Pathogens most often penetrate the plant through the root system and subsequently cause its death. An extensive branched mycelium develops inside the vascular system, as a result of which the affected plant dies. Fusarium wilt develops very quickly, in fact it occurs a few days after infection.

The disease is common in all climatic zones. In our country, it is most often found in the south, southeast or in the Far Eastern regions. On average, in the most unfavorable years, the yield of different crops can decrease by 40%.

Fusarium wilt of a cucumber at an early stage can be diagnosed by a drooping top during hot hours. If the disease proceeds in an acute form, then the plant withers completely and instantly. Suffering - the main rhizome dies off, but the lateral processes partially remain viable.

Y begins with a change in the color of the lower leaves. They become chlorotic and drooping. With the development of the disease, the color of the veins changes - they become brown. Gradually, all leaves begin to die, necrosis appears.

Fusarium wilt of strawberries begins with the death of tissues along the edge of the leaves and a slight wilting. Then the petioles and leaves turn brown, and the rosette loses its elasticity and falls apart. May cause rot in high humidity. Completely the plant dies in about 1.5 months.

In general, it can be noted that Fusarium wilt can appear at any stage of the plant's life cycle, but most often it occurs during the flowering period.

How infection occurs

The main source of infection is contaminated soil. Therefore, plants in greenhouses most often suffer, where the soil does not change and crop rotation is not applied. Another cause of Fusarium is infected seeds. Mushrooms develop and grow together with the plant, and then destroy it.

Fusarium wilt: prevention and control measures

Dressing the planting material will prevent the possibility of introducing pathogens into the seed bed. Good digging of the soil, loosening, changing the substrate, crop rotation and disinfection of the tool also lead to a decrease in the possibility of disease. Mushrooms develop well at high air temperature (about 28 ° C), high humidity and short daylight hours. Therefore, greenhouses must be well ventilated. As a preventive measure, it is necessary to inspect the beds once a week and identify the affected plants. Diseased specimens are removed and burned. Good results are shown by preliminary steaming of the soil and its disinfection with special biological preparations based on fungal antagonists. Of the chemicals, you can use Privekur.

A third example is Fusarium culmorum, which also infects the roots of seedlings of a wide variety of plants (asparagus, cereals). It is not found in the soil as a free mycelium, unlike Pythium and Rhizoctonia, since its spores germinate only in the presence of a suitable substrate. All these species belong to saprophytic "sugar" mushrooms. They preferentially infect young, already damaged or weakened roots and never disappear from the soils of cultivated fields.

Vessel-damaging fungi occur primarily in the Fusarium oxysporum group and among the Verticitlium species. Fungi that cause tracheomycosis penetrate the roots of the host plant, in which, however, they immediately germinate to conductive vessels (xylem).

This leads to the withering of plants, which occurs not as a result of mechanical blockage of blood vessels, but is caused by the action of fungal secretions on plants.

Fungi secrete, first of all, special wilt toxins (fusaric acid, lycomarasmin), which disrupt the osmotic functions of living cells, mainly in leaves. Secondly, they contain pectinase, which destroys protopectin, the main substance of the middle plates in the vessels. The pectic acids and other products of partial hydrolysis released in this way increase the viscosity of the xylem sap and thereby impede the supply of water.

Since the rest of the tissues of the host plant are resistant to wilting pathogens, only a few, less resistant vessels are affected. Only after the plant dies and the fungus leaves the conducting vessels, the affected root can infect neighboring roots. Forcibly removing a damaged plant leaves the infected parts of the roots in the soil, and the disease spreads even faster. The introduction of nitrogen fertilizers stimulates the development of fungi that affect the vessels, directly enhancing their nutrition.

Since fungi can exist as saprophytes, they do not disappear even when crop rotations are changed. Tracheobacteriosis is widespread, the causative agents of which can be, for example, Erwinia tracheiphila, Corynebacterium michiganense, Xanthomonas campestris or Pseudomonas solanacearum. These bacteria also contain pectinase and even cellulase, so the process of plant wilting proceeds in the same way as with fungal infection.

However, all these fungi can be in the form of resting spores (archymycetes, phycomycetes) or sclerotia (ascomycetes, imperfect fungi) for many years in the absence of their host, until a suitable fodder plant again appears.

Low temperatures, drought and poor soil aeration allow mushrooms to better tolerate the cold season. Similarly, dormant spores of cabbage club survive the longest in relatively dry, alkaline soils. Such conditions limit the possibility of spontaneous germination of spores, which in winter would naturally damage the fungi.

If during tracheomycosis the growth of the fungus inside the plant does not depend on the state of the soil, then for ectotrophic fungi that develop in the roots, soil conditions are always of decisive importance.

In addition, they only damage seedlings, so the period of possible infection is relatively short. In Ophiobolus mushrooms, the opposite is observed. True, the processes in the soil are so complex that it is quite difficult to foresee the impact of certain activities, such as fertilization. With each new combination of external factors, conditions can develop completely differently.