Phytopathogenic fungi significantly reduce the decorative effect, viability, as well as the yield and quality of production of food plant species, and in fruit trees and berry growers, in addition, reduce the terms of their economic use.
Fungal spores can persist for a very long time in post-harvest residues, in the soil, carried by wind, raindrops, animals and humans, containers, machines and tools. That is why it is so important to keep everything clean, and always carefully and carefully dispose of plant residues on your site.
The presence of various fungi on plants is evidenced by a change in the usual green color of leaves, the characteristic color of buds and flowers. And it also manifests itself in the appearance of a cotton-like growth on the wood of soft or softened areas on the plant, spots of different colors or a gray "fluff" on the leaves, black sooty spots or dusty red "spots", crossing gray "threads" of fungal hyphae on the soil surface. On diseased fruits, rotten leaves and rotten wood, fungi may appear as a loose "lace" or powdery mass, like a "film" or "crust", or have the form of plates or scales. Under the influence of developing fungi, plant tissues become covered with plaque, spots or atypical "veins". Then the parts of plants affected by fungi begin to die and decompose; or, conversely, twist, dry out, deform and become covered with cracks. The sooner diseased plants (or parts thereof) are identified, the easier and easier it is to deal with fungal diseases.
What can be done to, if not get rid of fungal diseases, then at least significantly reduce their likelihood. There is, for example, such a well-known agronomic technique as liming the soil. In this case, the soil is alkalized and thereby the risk of damage to plants (for example, cabbage - keel) is reduced. With a lack of boron in the soil, beets are more likely to get heart rot. Excessive application of nitrogen to the soil with a lack of phosphorus and potassium increases the damage to cereals by rust, and potatoes by late blight.
At home, a liquid for disinfecting plants, pots and plant care equipment can be prepared from a solution blue vitriol with the addition of one of the available insecticides. To obtain a disinfectant liquid, 2 g of Aktellik (or 1 g of Decis; or 1 g of Karate) is added to a 0.5% solution of copper sulfate (5 g per 1 liter of water). You can use an aqueous solution (0.1–0.2%) of potassium permanganate (potassium permanganate) to process inventory, spring processing soil.
Prolonged rains and high soil moisture, stagnant moist air in dense plantings often lead to fungal diseases. garden plants. One of the preventive methods is to keep the garden clean. You should regularly collect all the carrion, and at the first sign of infection with fungal diseases, immediately begin to treat diseased plants. Severely diseased specimens that cannot be treated must be burned.
When propagating plants and caring for them, charcoal and other means are used to prevent the penetration of pathogenic fungi into plant tissues. Growth bioregulators, such as Energen, help strengthen plant immunity. Energen increases the yield by 30-40%, stimulates the growth and development of plants, protects against adverse factors, frost, drought, increases the survival rate of plants during transplantation, and also reduces the content of nitrates in fruits.
If the plants are still sick, then you have to resort to treating them with suitable fungicides, or, in order to avoid rapid infection and the death of many plants. especially in the collection, destroy diseased specimens.
Essential oil, in the form of spraying, or treating plants with an alcoholic solution of essential oil (1:100), has a powerful effect on the reproduction and spread of harmful fungi. Pronounced antifungal properties have essential oils oregano, thyme, monard, lavender, patchouli, hyssop, marigold, eucalyptus, cedar and some other plants. Alcoholic extracts of such plants as onion, garlic, marigold, yarrow, tansy, which are prepared in a ratio (1:10, and then, before use, also diluted in water 1:10), can be used as an antifungal agent.
Plant diseases caused by fungi
BLACK LEG is the most common disease that affects seedlings and seedlings of most crops. With the defeat of the "black leg" in young plants, white, subsequently turning brown and decaying spots and constrictions are formed in the lower part of the stem, as a result of which the plants wither and die.
ROOT ROT - often affects adult plants: they begin to lag behind in growth, turn yellow, and then partially or completely die. Species affected by root rot should not be planted in soil in which fresh manure has been introduced, as well as in places where plants affected by this disease have been in previous years.
Fusarium wilt - brown necrotic spots appear on the leaves and stems. The plant stuns and then dies. Plants of the same species cannot be planted in their place for several years. In the seedling phase, rotting of the roots, the stem at the root collar and cotyledons is observed. Seedlings turn brown and often die before reaching the soil surface.
POWDER - A white powdery coating appears on the lower and / or upper side of the leaves and petioles, and then dark dots.
PERONOSPOROSIS or false powdery mildew widespread in areas with sufficient moisture. The disease affects all aboveground organs. The disease manifests itself in two forms: general inhibition of plants (diffuse lesion) and leaf spot (local lesion).
RUST - widespread. The disease often manifests itself in the second half of the growing season. The disease develops most strongly in warm and humid years.
Fungicides - drugs used against fungal diseases
These preparations are divided into a number of groups: inorganic (preparations based on sulfur, copper and mercury) and organic. They are divided into preventive (stop the development and spread of the pathogen in the place of accumulation) and therapeutic (cause the death of the fungus after it infects the plant). Fungicides can also be contact and systemic. Contact fungicides, when treated with plants, remain on the surface and cause the death of the pathogen upon contact with it. The effectiveness of contact preparations depends on the duration of action, the amount of fungicide, the degree of retention on the treated surface, photochemical and chemical resistance, weather, etc. Systemic fungicides penetrate the plant, spread through the vascular system and suppress the development of the pathogen due to direct exposure to it or as a result of plant metabolism. Their effectiveness is mainly determined by the rate of penetration into plant tissues and to a lesser extent depends on meteorological conditions. The nature of the use of fungicides is different: seed dressings, for soil and plant treatment, both during the dormant period and during their growing season.
With the systematic use of the same fungicides, their effectiveness may decrease due to the formation of resistant races of the pathogen. To prevent this phenomenon, it is necessary to strictly observe the doses of the drug and alternate fungicides.
Biological fungicides: Fitosporin, Barrier, Zaslon, Fitop, Integral, Bactofit, Agate, Planzir, Trichodermin. Biological fungicides are characterized by low toxicity and high efficiency.
Acrobat M, Ditan M-45, Ridomil, Sandofan - have a systemic, penetrating and contact action, acting against a wide range of phytopathogenic fungi.
Bordeaux liquid (one of the most effective and oldest remedies) is effective in combating rust, gray mold, spotting, late blight, scab and downy mildew. For spraying plants during the growing season, a 1% solution is used; for spraying woody plants before bud break, a 3-5% concentration is used.
Gliokladin - An analogue of Trichodermin. Biological fungicide for the suppression of pathogens of fungal diseases in the soil.
Potassium permanganate (potassium permanganate) is used for dressing seeds, bulbs, corms, rhizomes of plants at a concentration of 0.1–0.15% for two hours. It can be used for health-improving watering of seedlings, seedlings and adult plants under the root in the fight against blackleg, fusarium, bacteriosis. It is used for disinfection of stock and tools.
Oksihom has contact and systemic activity. It has a destructive effect on pathogens in all stages. Provides a long-term therapeutic and preventive effect.
Soda ash (linen) is used to combat powdery mildew. For spraying, a 0.3–0.5% solution is prepared. For better adhesion to plants, laundry soap is added to the soda solution.
Tattu enhances the immune system of the plant, is well tolerated by plants during the entire growing season.
Tilt, Topaz, Skor, Bayleton, Alto, Impact, Vectra - have a systemic, penetrating and contact action, acting against powdery mildew and rust fungi.
Trichodermin. Biological fungicide for the treatment and prevention of plant root infections. The mycelium of the fungus germinating in moist soil from spores suppresses about 60 types of soil pathogens that cause root rot.
Fitosporin-M is a microbiological preparation designed to protect plants from a complex of fungal and bacterial diseases.
Fundazol is a fungicide and disinfectant with a wide range of systemic action against a large number of fungal diseases of seeds and plants.
Copper chloride is effective against the same diseases as Bordeaux liquid. Used in 0.4–0.5% concentration. Do not add soap to the working solution.
When purchasing fungicides, instructions for use are always attached to them. It is very important to strictly follow the dilution prescription, the use of recommended doses, the timing and rules of use.
Alexey Antsiferov, Candidate of Agricultural Sciences,
corresponding member of ANIRR
A third example is Fusarium culmorum, which also infects the roots of seedlings of the most various 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 every new combination external factors conditions may be quite different.
Plant diseases caused by fungi:
Viral diseases:
1. Powdery mildew
Description: On the surface of the leaves of the affected plant appears white coating mycelium, on which, after maturation of spores, drops of liquid form - hence the name "powdery mildew". Mycelium is located in spots most often on leaves and young shoots, but also on petioles, stalks and fruits. The infection usually begins with leaves located closer to the ground and gradually spreads to the entire plant. Infection of fruits leads to their cracking and decay. In rainy summers, it is often not possible to prevent plant diseases even when good prevention has been carried out. Unlike other mushrooms, it develops in rainy and dry weather. It is carried by spores by wind and insects.
Prevention: For the prevention of powdery mildew of roses and euonymus, it is good to carry out pollination with sulfur 3-4 times during the summer. Overfeeding plants with nitrogenous fertilizers, especially during the budding period, increases the risk of powdery mildew. On the contrary, top dressing with phosphorus and potash fertilizers increases the resistance to the powdery mildew pathogen. Cut off and burn infected plant parts. Avoid strong anti-aging pruning that weakens the plant.
Control measures: If several leaves or buds are affected, they must be removed. Spraying every 5-7 days with special biological preparations to combat powdery mildew, as well as potassium permanganate(2.5 g per 10 liters of water), 0.5% copper chloride, 1% colloidal sulfur(30-40g \ 10l) (except gooseberries!), a mixture of soda ash and soap(for 10 liters of water 50 g of soda and 40 g of soap).
You can use drugs such as topaz, vectra(2-3ml\10l) "fast"(2ml\10l) "Cumulus"(20-30g\10l) "strobe"(2-3ml\10l), "thiovit"(20-30g \ 10l) (cucumbers, zucchini). It helps well with powdery mildew by spraying with a mixture of antibiotics: terramycin 100 units / ml, penicillin 100 units / ml and streptomycin 250 units / ml in a ratio of 1: 1.
Spray plants with a solution in summer soda ash (linen) with addition laundry soap(50 grams of soda and 40 grams of soap per 10 liters of water). Spraying is repeated after 8-10 days.
TO biological methods powdery mildew control is infusion of rotted manure, better than cow's (one part of the manure is poured with three parts of water and insisted for three days, then the infusion is diluted two or three times with water, filtered and sprayed). Treatment with infusion is carried out several times, preferably in the evening. Bacteria in manure kill powdery mildew spores.
Spraying plants with mixed infusion of mullein and ash(for 10 liters of water 1 kg of manure and 200 grams of ash, insist a week in a warm place, stirring occasionally, filter and spray). The same measures can be applied to control powdery mildew on gooseberries and blackcurrant, other berries. Two weeks before harvest, all treatments are stopped.
2. Downy mildew or downy mildew.
Description: It affects the green parts of the plant, mainly the leaves. Spots form on the diseased parts of the plant, on the underside of which a whitish, grayish or purple coating appears - sporulation of the fungus (zoosporangia with sporangiophores). Zoosporangia can occur multiple times during the growing season: spread by air, they serve as the main source of infection. The development of the disease is favored by high air humidity and soil. In most pathogens, the mycelium is one-year-old, dying off along with the infected parts of the plant, but it can also be perennial, remaining in bulbs, roots, and other overwintering organs.
Prevention: Maintaining low humidity, regular airing, thinning and cleaning the bushes. Change of soil and its disinfection. If signs of the disease are already detected, avoid spraying and watering the leaves when watering.
Control measures: Careful removal of diseased leaves and severely affected plants. Spraying plants with a 1% solution of Bordeaux liquid or soda ash (0.5%), especially carefully the underside of the leaves. You can use copper oxychloride (40g \ 10l), "abiga pig"(20g\10l), "oxychom"(20g\10l), "kuproksat", "kartotsid"(30-40g\10l), "kursatr"(50g \ 10l),. Start treatment at the first sign of the disease and repeat every 7-10 days. At least 5 treatments are required.
3. Moniliosis (Monilia) or fruit rot or monilial burn
Description: fungal disease, called ascomycetes Mo nilia . Widely distributed in temperate climates, especially in areas with cold, wet springs, it affects mainly stone fruit and pome crops. Plants are infected with moniliasis mainly through damage to the bark. Plant damage occurs during flowering. After incubation period lasting 10-11 days, the affected leaves and inflorescences turn brown, wither and die. Affected fruits mummify and fall off (or remain hanging on branches during the winter); the fungus overwinters in affected fruits.
Prevention: It is important to carry out preventive measures to combat caterpillars, codling moths, weevils, goose and other pests and diseases. When harvesting, care must be taken not to cause mechanical damage to fruits and berries. The development of gray rot is restrained by whitewashing boles and skeletal branches of fruit trees, carried out in late autumn.
Control measures: It is necessary to regularly collect and destroy the affected fruits, remove dead branches. In gardens, trees and soil are sprayed liberally nitrafen, iron vitriol, copper sulphate, oleocuprite or 1% Bordeaux liquid Yu. Spraying is carried out before flowering. The second spraying is carried out immediately after flowering 1% Bordeaux liquid(100 g per 10 liters of water) or solutions cineba, copper chlorides, captan, phthalan, cuprosane and other fungicides.
When using drugs copper oxychloride and Bordeaux liquid for summer spraying, you must first make sure that they do not cause leaf burns. For verification, control branches are selected and only them are sprayed. Burns appear as necrotic spots on leaves or nets on fruits.
And: Horus, Abiga-pig, Planriz, Speed.
Moniliosis-resistant apple tree varieties: Parmen winter gold, Ranet Simirenko, Jonathan, Pepin saffron, Welsey.
4. Spotting
Description: In a plant with spotting, spots appear on the leaves various shapes, size and color. Quite often, the spots are bordered by rings of one color or another. In some cases, stains are chipping. One of the varieties of leaf spot is septoria. On different parts plants are formed different kind, colors and shapes dying areas (spots) of tissues. The bark cracks, gum exudes from the wounds. There are especially many spots in dense gardens. The infection persists on plant debris, weeds and in the soil. The spores of the fungus are carried by water, wind, insects, animals and humans, when they move from diseased plants to healthy ones during work.
Azalea: Yellowish spots appear on the leaves of the diseased plant, with the further development of the disease they turn brown. The leaves turn yellow, but green borders remain around the spots on the leaves. In the future, the foliage flies around. Black dots are visible on the spots, which are pycnidia of the fungus. Plants are most often affected with improper agricultural practices, serious errors in care.
For irises: Initially, oval or oblong yellowish spots appear on the leaves, later their color becomes light brown, with a pronounced dark strip along the edge of the spot. Later, a blackish coating appears on the spots, mainly in the middle. The leaves turn brown, dry out, as the disease covers the entire plate. The fungus overwinters on infected plant debris.
For phloxes: Initially, reddish-violet spots of a rounded shape, about 2-4 mm in diameter, form on the lower leaves. After the spots spread to the upper leaves. As the disease develops, the spots turn white in the center, forming small numerous dark-colored pycnidia. The spots later merge, causing the leaves of the plant to dry out. The fungus successfully overwinters in infected leaves.
At the viola: the causative agent of the disease is a fungus Colletotrichum violae tricoloris . When affected by this fungus, small rounded yellowish-brown spots appear on the leaves of the plant, with a pronounced dark border. Over time, the spots increase. If you look at the spots in a magnifying glass, you can find dark pincushion-shaped formations.
Control measures: The main measure to combat spotting is timely agricultural practices, cleaning the area from foliage and plants in the fall, as they are sources of infection. Correct Mode watering, lighting and fertilizing creates optimal conditions for plant growth, and in strong specimens, fungal spot damage does not cause such serious consequences as in plants grown with care errors. Timely application fungicides also significantly reduces the damage from fungi that cause spotting. In the spring, before bud break, treat the plants with 3% Bordeaux liquid, and before flowering and after harvesting - 1% or blue vitriol.
5. scab
Description: The causative agent of scab overwinters on fallen leaves. Spores are picked up by the wind and fall on the young leaves of apple and pear trees. If there are water droplets on the leaves, the spores can germinate. In spring, small light green oily spots appear on young leaves of diseased trees. Later they are covered with a brownish-olive velvety coating. Rounded dark spots with the same bloom are formed on the fruits. In places where the fetus is affected, the tissues cork, crack and rot. Scab of an apple tree does not affect a pear and vice versa!
Prevention: Create a good air and light regime in the garden and in the crowns of trees. Don't apply too much nitrogen fertilizer.
Control measures: Treat diseased trees Bordeaux mixture: the first time in the green cone (4%) or budding (2%) phase; the second time immediately after flowering (1%); third time 2 weeks after the second treatment (1%). This spray is called "blue", as the trees take on a bluish color. In autumn, spray the soil under the crowns of trees and fallen leaves with a 7% solution. urea or 10% solution ammonium nitrate. Instead of "blue" spraying during the budding of apple and pear trees, you can also use 1% Bordeaux liquid (100 g of copper sulfate and 100 -150 g of lime).
Against scab, apple and pear are used and copper oxychloride, 90% wettable powder (30-40 g); polycarbacin, 75% s. p. (40 g) or polychom, 80% s. item (40 g). Bordeaux liquid and other copper preparations in wet weather can cause leaf burns, therefore, in such years, 5 days before treatment, individual branches of trees of all varieties should be sprayed to check for scorching.
Fallen leaves are collected and burned in autumn!
6. Anthracnose
Description: Plants affected by anthracnose are covered dark spots, ulcers; ulcers are sometimes surrounded by a purple border, the spots themselves are more often brown, although they can also have a pinkish, orange tint; as the disease develops, the spots on the leaves merge, the leaves turn brown, dry out and fall off prematurely. Anthracnose covers the entire aerial part of the plant, developing on leaves, stems, shoots and fruits. Anthracnose-infected fruits rot.
Signs of defeat: All above-ground organs of the plant are affected. The disease usually begins with the defeat of the leaves, which form brown spots with a darker border, first along the edge, then the spots gradually merge. Depressed spots form on the branches of the stems, which disrupt the movement of nutrients through the plant. Symptoms of the disease on the shoots: light brown oblong spots that gradually expand, deepen, darken and are bordered by a dark purple or brown rim. In dry weather, cracks appear on the affected areas, with high humidity stems rot and break. With a strong development of the disease, the leaves completely turn brown and dry out, the entire aerial part of the plant dies. The development of the disease is promoted by high humidity, high soil pH, lack of phosphorus and potassium.
Prevention: The disease can be spread by sprayed raindrops, irrigation water, insects, equipment and inventory. Warm, humid weather favors disease development. Observe the humidity regime in the room; in summer, during prolonged wet weather, try to keep the plant indoors without exposing it to open air keep an eye out for pests. Use calcined earth. In preventive measures, it is allowed to spray the plant with cuproxate, copper oxychloride, and oxychom.
Control measures: If the plant is not severely infected, carefully remove the diseased parts. Spray with fungicides (kuproksat, copper oxychloride, oksihom, sandofan M8, acrobat MC and other similar preparations) 2 - 3 times.
7. Phyllosticosis
Description: Dark rounded or oval spots appear on the leaves with a darker border along the border with healthy tissue. Often the affected tissue falls out and the leaf becomes perforated.
Prevention: Contribute to the development of diseases violations of the conditions of detention, as a rule, warm and humid conditions, therefore, plants in greenhouses, and not in rooms, are most often affected. Avoid large crowds of plants and over watering. Ventilate the room regularly and provide good lighting. Water the plants using Fitosporin-M. Remove any leaves that begin to dry out. If a part of the leaf is cut off, then by all means it is necessary to capture a part of healthy tissue.
Control measures: Removal and burning of diseased leaves. Treatment with a systemic fungicide. Reduce watering, airing, cancel spraying for several weeks. If suspicious spots have already appeared on the leaves, cancel spraying with plain water. You can use drugs: Vectra (2-3ml per 10l of water), colloidal sulfur (50-100g per 10l of water), strobe (in a system with other fungicides, 4g per 10l of water), Abiga-Peak (40-50g per 10l of water) , Bordeaux mixture (100g copper sulfate + 100g lime per 10l of water), copper sulfate (500g per 10l of water). Repeat the treatment after 7-10 days.
8. Coccomycosis
Description: Coccomycosis affects the leaves and fruits of cherries, plums and other stone fruits. The fungus overwinters on fallen leaves. In the spring, the wind carries the spores. First, reddish-brown dots appear on the surface of the leaves, then they merge and grow into spots. A white-pink bloom forms on the underside of the leaves. In late July, diseased trees can shed up to 80% of their leaves. Depressed brown spots with a whitish bloom appear on the fruits.
Control measures: Treat the plants Bordeaux mixture: the first time in the green cone phase (4% solution) or budding (2% solution), the second time immediately after flowering (1% solution) and the third time after 2 weeks (1% solution). In the fall, spray the soil under the crowns of trees and fallen leaves with 7% urea solution or 10% solution ammonium nitrate.
To combat coccomycosis (its pathogens also persist in last year's leaves during the winter), at the beginning of the bud break of cherry trees of unstable varieties, they also spray 1% Bordeaux liquid or copper chloride at the indicated concentrations.
Bordeaux liquid and other copper preparations in wet weather can cause leaf burns, therefore, in such years, 5 days before treatment, individual branches of trees of all varieties should be sprayed to check for scorching.
In years with a dry spring, the need to combat scab and other moisture-loving plant pathogens in the period from bud break to tree flowering disappears.
9. Cytosporosis
Description: Cytosporosis - this disease is transient and chronic. In the first case, reddish-brown and yellow-brown spots appear on the bark. irregular shape. Gradually, they grow and ring the branch, which soon dries out. The tree can die in 2-3 years. In the second case, tubercles appear on the surface of the reddish-brown bark. The bark resembles goose skin. The wood is dying. Separate small and large branches dry out.
Protection: Avoid damaging the bark. When wounds appear, disinfect them with 3% copper or iron sulphate and cover with garden pitch.
Prevention: Avoid damaging the bark.
Control measures: If wounds appear, disinfect them with 3% copper or iron sulphate and cover garden pitch.
10. Verticillosis or wilt
Description: The plant is affected through wounds on the roots and stems - the fungus remains in the soil. As with Fusarium, the disease is manifested by loss of turgor and withering of shoots. On transverse sections of plant stems, browning of conducting vessels is also noticeable. But first, as a rule, the lower leaves turn yellow and droop, as if the plant was flooded. Then I begin to wither the upper leaves and the whole plant. Plants lose decorative look. In the acute course of the disease, the plant suddenly withers and dies in a few days. Wherein obvious signs the disease is not visible, and only a brown ring of nutrient vessels on the cut of the stems can serve as evidence of the disease.
Control measures: Possible only in the initial stages, by spraying foundationazole, vectra or topsin-M at a concentration of 0.2%. - do not allow waterlogging of the soil, do not use excessive doses of nitrogen fertilizers, do not allow wounding of roots thicker than 3 mm during the next tillage.
11. Gray rot
Description: They are mainly affected in protected ground. Flowers, leaves, stems, fruits are affected. First of all, weakened plants can be affected, the clinical picture manifests itself at the beginning on the lower aging leaves, then the pathogen spreads to the stem. Light brown dry spots form on the stem. The defeat of the fruit begins with the stalk, then a spot appears gray color, quickly covering the entire fruit, its surface becomes watery and covered with a gray fluff (conidial sporulation).
Prevention: Regular ventilation of the premises, removal of dying leaves and thinning of seedlings, good lighting. Avoid waterlogging the soil, especially when kept cool. It is advisable to avoid getting fertilizers with a high concentration of nitrogen on the leaves. Too much nitrogen causes the cell walls to soften, making these tissues susceptible to infection.
Careful handling of the plant during its formation, especially when removing leaves, reduces the wound surface and, thereby, reduces the number of foci of rot. Cutting out damaged sections of stems and stalks is carried out with a sharp knife in dry weather. All plant residues must be removed without fail, as they can become a source of infection for the plant.
Control measures: At the first sign of the disease, diseased leaves, inflorescences and whole plants are removed. Spraying with a solution topsina-M (0,1%), foundationazole (0,2%), copper soap solution(0.2% copper sulfate and 2% laundry soap) or other systemic fungicide. Repeated treatments are carried out after 10-12 days.
In case of weak infection, you can spray with Bordeaux liquid or preparations. Topaz, Oksihom, Champion, Kuproskat. To combat gray mold, you can use the drug Integral. You can also use drugs such as Kartocide, Skor. When foci of gray rot appear on plants, some practice coating the affected areas of the stems with a paste of glue based on CMC and trichodermin. Severely affected areas are pre-cut with a sharp knife.
12. Rust
Description: It is expressed in the appearance of orange-brown tubercles on the upper surface of the leaf, and pustules, oval or round, are visible on the reverse side of the leaf. Gradually, the spots develop into stripes, the leaves turn yellow and fall off. Amazes many ornamental plants And vegetable crops. There are different types of rust, depending on the causative agent of the disease.
Prevention: Like other fungal diseases, rust appears at high humidity, so prevention consists in uniform watering.
Control measures: The best remedy Rust control is prevention. Don't pour water on the leaves. Remove affected leaves and branches. Clean tools with alcohol. Collect fallen leaves around the infected plant. Apply spraying preparations: "topaz", "vectra", "strobi", Bordeaux mixture, cuproxate. The treatment is repeated 2-3 times in 10 days.
13. Late blight
Phytophthora of tomato: Southern late blight of tomato affects both seedlings and adult plants. Constrictions form on the stem, watery rot with concentric zones from gray to red-brown on the fruits. At high humidity, a white mycelium appears on the fruits.
Control measures: The main attention should be paid to the prevention of late blight, not only during the growing season, but also in the off-season. After harvesting, plant residues should be collected and buried in a specially designated place. Dig up the soil to a depth of about 20 cm. In greenhouses and greenhouses, it is recommended to replace the topsoil. If possible, the circulation of crops should be observed - the tomato should be returned to its original place no earlier than after 4 years. Before sowing, it is recommended to treat the seeds with a 1% solution of potassium permanganate (1 g per 100 ml of water) for 20-25 minutes, followed by washing and drying; feeding seedlings with phosphorus-potassium fertilizers; during the growing season - treatment with a copper-soap emulsion (2 g of copper sulfate and 200 g of soap per 10 l of water; treatment of plants with garlic with potassium permanganate (1.5 cups of garlic pulp, 1.5 g of potassium permanganate per 10 l of water); watering plants with a solution consisting of 40 drops of iodine and 30 g of potassium chloride per 10 liters of water (0.5 liters per 1 plant).If the temperature drops at night and there is a threat of a strong development of late blight, green fruits are removed, disinfected in hot water(60°C for 1.5-2 minutes or at t 40-45°C - 4 minutes) and after drying, ripen in the dark at a temperature of about 25°C.
Apple Phytophthora: It mainly affects the root neck of trees, where the bark acquires a blue-violet color and cracks, under the bark the tissue is dark brown (chocolate brown).
Control measures: Collecting and destroying carrion on which the fungus overwinters, treating trees by cleaning and disinfecting wounds, or burning affected areas. Copper-containing preparations of contact or combined action (copper sulfate, kuproskat, oksikhom, etc.) can help as preventive measure. Timely spraying reduces crop losses from late blight.
14. White rot
Description: It affects all parts of plants: stems, petioles, leaves, mustaches, fruits. Affected tissues become soft, slimy, covered with white mycelium. Black dots form on the surface and inside the stems. In plants affected in the basal part, the leaves wilt and dry out. Only an examination of the stem allows us to establish that the cucumbers died as a result of white rot. Plants are most susceptible to disease in the fruiting phase. The development of the disease is facilitated by increased humidity of the soil and air, sharp temperature fluctuations, dense plantings. In addition to cucumbers, the disease affects tomatoes, parsley, eggplant, pepper, cauliflower. Therefore, after these crops, cucumbers cannot be grown.
Control measures: Compliance with the rotation of cultures. Lime powder on stem areas with signs of disease. Cutting out the affected parts of plants with a part of healthy tissue. With a strong spread of the disease, remove the leaves during the hot, dry hours of the day (so that the wounds dry out faster). Sprinkling the cut with crushed coal or wiping with a 0.5% solution of copper sulphate. Evening watering warm water and periodic ventilation of greenhouses. The use of foliar dressings (1 g of zinc sulfate, 2 - copper sulfate and 10 g of urea). Watering in the wells when planting seedlings of cucumbers with a solution of potassium permanganate (5 g).
15. Sooty fungus (black)
Control measures: Timely spraying from pests that form sweet secretions. Wipe affected plants with a sponge dipped in soapy water and treat with a systemic fungicide against pests. It is possible to carry out the treatment with a copper-soap solution (0.2% copper sulfate and 2% laundry soap).
16. Vascular (tracheomycosis) wilt
Description: The disease begins with root rot. Pathogens penetrate from the soil, first into small roots, then, as the mycelium grows, into larger ones. Then, along the conductive vessels, they rise into the stem and reach the leaves. The lower leaves wither, the edges of the rest become watery, and some areas are pale green or light yellow. Vessels of leaves and petioles weaken, and sluggish leaves hang along the stem. At temperatures below + 16 ° C, diseased plants die quickly enough. At the same time, fungi secrete toxins that cause decomposition of cell tissues, root rot, browning and drying of branches and leaves. With increased humidity, a delicate white coating forms on the surface of the leaves.
Control measures: At the initial stage of the disease, you can try to cure the plant. For this, spraying with one of the preparations is used: Vitaros, Benlat, Fundazol, Previkur, Topsin-M at a concentration of 0.2%.
If the plant is seriously ill, it should be destroyed.
17. Black leg
Description: This disease most often manifests itself in greenhouses in the process of forcing seedlings of cabbage, tomatoes, eggplant, pepper. In plants, the root neck is mainly affected. This is manifested in its darkening, the stem in this place becomes thin, the plant breaks and soon dies. Plants drop out of the development cycle in patches. The disease proceeds more intensively with thickened crops, when humidity and temperature are elevated. The infection remains in the soil.
Control measures: Change the soil in the greenhouse every year. Maintain optimal planting density. Maintain normal humidity and temperature in the greenhouse by timely ventilation. It is necessary to remove diseased plants in the foci where the black leg develops or to treat them with 1% Bordeaux mixture at the rate of 1 liter per 1 square meter, followed by adding a layer of sand to them, a layer of 1 centimeter to form new additional roots above the damaged area. Also, when a black leg appears, you can water the seedlings with a solution of potassium permanganate (0.1 grams per 1 liter of water) or HOM (copper oxychloride), at the rate of 40 grams per 1 liter of water. An effective method of combating black leg plant disease is seed dressing before sowing with fentiuram (65% wetting powder), at the rate of 4 grams per 1 kilogram of seeds, or TMTD (80% wetting powder), at the rate of 8 grams per 1 kilogram of seeds. Before starting treatment, the seeds must be moistened (10 milliliters of water per 1 kilogram of seeds). Moderate watering of seedlings. Disinfect the soil by heating it in the oven for 30 minutes at a temperature of 110 degrees. After that, you can sprinkle the soil "colloidal gray", at the rate of 20 grams of powder per 10 liters of water. The soil for seedlings should not be very acidic. Seedlings must be culled before planting in the garden.
Viral diseases
18. Jaundice
Description: Pale green color of the leaves of the plant, in some cases - and shoots, also their increased branching, the appearance of a large number of buds, from which, however, deformed flowers are obtained. The petals of the plant turn green, in some cases parts of the flower change their shape, with a pronounced tendency to turn into a leaf. Plants affected by jaundice usually do not form seeds.
In some cases, as the plant grows, chlorosis captures new leaves and all green above-ground parts of plants. Young leaves become almost white in color. In diseased plants, growth retardation of the main shoot is often observed. With the development of the disease in the tissues of the stem, necrotic spots begin to appear, causing the death of the affected areas. Thin shoots of the second order can form in the axils of the leaves. Also, sometimes a sign of the disease is a change in the direction of the leaves - they are arranged in a vertical direction.
Control measures: Unfortunately, chemicals cannot effectively fight against viral diseases. The only way to fight is to prevent the disease, which includes both active with sucking insects, which, as a rule, are carriers of pathogens, and keeping the plantings clean, regular weeding, and high-quality agricultural technology.
If the plant is already affected by the virus, then it remains to remove all the affected parts of the plant. After work, wash your hands thoroughly with soap and wipe the equipment used with alcohol. Cuttings should only be taken from healthy plants.
Bacterial plant diseases
19. Bacterial blotch
The spots appear as a result of the necrosis of leaf areas, but unlike the spots caused by fungi, these spots do not have such pronounced borders - they have blurry edges. The spots may be glassy or oily. The spots usually grow rapidly in size, the leaf may dry, turn yellow and then die. Warm, humid conditions favor faster spread of the disease.
20. Bacterial necrosis or cancer
Description: Abnormal growth of quite healthy-looking plant tissues. Tumor growths form on the roots and sometimes on the stems. With a strong development of these growths, the plants grow poorly and eventually die.
Root bacterial cancer. Small, soft, tumor-like outgrowths appear on the roots and root collar. smooth surface. Then they grow, harden, their surface becomes bumpy. In autumn, growths can collapse. Pathogens remain in the soil and remain viable for 3-4 years.
Protection: Do not use seedlings with signs of cancer for planting. In the place where the causative agent of cancer is located, do not grow plants susceptible to this disease for four years.
21. Nectrium (tubercular) necrosis.
Description: The fungus causes the formation of local and ring necrosis of branches and trunks, without changing the color of the affected bark. Fungi - causative agents of necrosis - infect both weakened and viable trees of many tree and shrub species of different ages. Starting from early spring, sporulation of the pathogen - stroma - is formed in the cracks of the bark. They are plexuses of mycelium, on the surface of which spores develop. Stromas are a characteristic sign of the disease and have the form of numerous, convex, smooth, pink or brick-pink pads with a diameter of 0.5 - 2 mm and a height of up to 1.5 m, arranged in rows or randomly. The duration of the disease from infection to death of trees ranges from several weeks to several years.
Control measures: Timely removal of shrunken branches. Spraying in the spring before the leaves bloom with copper-containing preparations.
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 on cucumber 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 lateral processes remain partially 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 occur 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
Etching planting material 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 thrive well high temperature air (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 shows the preliminary steaming of the soil and its disinfection with special biological preparations based on fungal antagonists. From chemicals you can use "Privekur".
IN practical work plant diseases are usually classified according to crops or their closely related groups. Within each culture, diseases are subdivided according to the etiological principle, based on the causes of their occurrence.
Non-infectious diseases are called diseases caused by unfavorable environmental factors: high or low temperature, lack or excess of moisture and nutrients, unsatisfactory physical and chemical composition of the soil, the presence of harmful impurities in the air, etc. These diseases are discussed in detail in the manuals on plant physiology, agrochemistry, agriculture and therefore are partially covered in the atlas.
Forms of manifestation of diseases are very different, which greatly complicates their recognition (diagnosis). Often, completely different diseases have similar external signs and, conversely, the same disease manifests itself differently depending on environmental conditions, the affected organs, the stages of development of the affected plant and pathogen, as well as the nature of the relationships that develop between them.
In practice, various external signs (symptoms) of diseases are grouped into separate types, which makes it possible to make a correct diagnosis of the disease.
The most common types of diseases are: wilting, tissue death, or necrosis, destruction of individual plant organs, rot, formation of plaque, growths, the appearance of pustules (pads), deformation of plant organs, mummification, gum secretion, discoloration of plants.
Withering externally manifested in the drooping of leaves, stems and other plant organs. In most cases, it is associated with the loss of turgor of cells and tissues due to lack of water. The reason for this may also be the blockage of plant vessels by pathogens or damage to them by toxins. Often, the plant withers when the roots and stems are affected by both pathogens and pests. The cause of wilting may be adverse environmental factors.
dying off tissues, or necrosis, are characterized by the formation of spots on the leaves, stems, reproductive organs, roots. The spots are of various sizes and colors, often surrounded by a border. Often they can see plaque or other pathological formations.
Rotten manifested in the softening and decomposition of plant tissues. In this case, the intercellular substance is often destroyed, as a result of which maceration (separation) of cells occurs.
raids on plant organs are observed in fungal diseases. Often they appear due to the growth of mycelium on the surface of the affected plants or the formation of sporulation of fungi. The color of the plaque is different.
Pustules it is customary to call convex pads of various sizes and colors, which consist of sporulation of the pathogen. Most often they appear with the development of rust diseases.
Deformation characterized by a change in the shape of plant organs under the influence of the pathogen. In this case, the leaves and stems can be shortened, strongly branched or fused. Sometimes the shape of the flowers changes, and they become barren.
growths, or tumors, appear due to the abnormal growth of individual parts of plants under the influence of the pathogen. There are also growths consisting of the body of the fungus.
Mummification- a type of disease in which the plant organ is densely permeated with mycelium and often turns into sclerotium.
Selection gums observed when plants are damaged mainly by fungi and bacteria. It is characterized by the release of sticky mucus of a light or brown color. Sometimes gum disease is caused by damage caused by agricultural implements and pests.
Change colors tissue is more often observed on leaves, stems and inflorescences under the influence of pathogens, especially viral and mycoplasmal ones, as well as in violation of plant nutrition. This phenomenon can also be caused by genetic diseases. A change in the color of tissues is associated with a violation of the structure and physiological functions of chloroplasts. This type of disease manifests itself in the form of chlorosis, mosaic leaves, variegation of color and general yellowing.
Asymptomatic(latent) diseases are more common when plants are damaged by certain viruses and mycoplasmas and are characterized by the absence of external signs of the pathological process. Latent diseases can be the cause of poor fruit formation. Sometimes there is a temporary disappearance of the symptoms of the disease, especially in hot weather, but when it gets cold they reappear.
It should be noted that listed types diseases are not limited to all the variety of manifestations of pathological changes in plants. In phytopathological practice, there are often cases when the external signs of several diseases are almost the same, but the causes of their occurrence and pathogens are different. Therefore, in order to accurately determine the disease, in addition to an external examination of the affected plant, special studies are needed to identify the pathogen and sources of infection. In most cases, the external signs of the disease are supplemented by microscopic studies and morphological data on the pathogen. In some cases, methods of fixing and staining sections of affected tissues are used for histological and histological-chemical studies.
To more correctly determine the pathogen and identify sources of infection, cultural and biological studies are often used.
Cultural studies of the causative agent of the disease consist in isolating it into a pure culture, studying it according to morphological and biochemical characteristics, as well as biological characteristics.
Biological studies are carried out when studying the specialization of the pathogen in relation to the affected plant and determining the degree of susceptibility of the latter to the pathogen. In these cases, artificial infection of plants with a pathogen is carried out, followed by a comparative study of the symptoms of the lesion and other features of the course of the disease. Great help in this matter is provided by knowledge of the physiological and biochemical characteristics of a diseased plant. It is also important to establish the factors that contribute to or hinder the development of the disease.
Mushrooms. Previously, they were considered an independent department of the plant world. Currently, researchers classify mushrooms as part of the kingdom of living organisms. Mycota, occupying an intermediate position in taxonomy between animals and plants.
They are brought closer to the animal kingdom by the presence of urea in the metabolism, chitin in the cell membranes, and the formation of a reserve product, glycogen. However, according to the method of nutrition (absorption, not ingestion of food) and growth characteristics, they are closer to plants.
All fungi belong to heterotrophic organisms, that is, they are not able to synthesize organic compounds and feed on various organic substances found in nature.
Mushrooms that settle on dead plants or other organic debris are called obligatory saprophytes. Many of them contribute to the cycle of substances in nature and are therefore useful, others can settle on agricultural products and spoil it.
Depending on the structure of the vegetative body, fungi are divided into two sections - Myxomycota And Eumycota(Hawksworth et al., 1983). In Myxomycota, the vegetative body consists of a protoplasmic amoeba-like mass. Most representatives of this department are saprophytes, living mainly in forests (mucus molds). However, among them there are also pathogens of dangerous diseases of cultivated plants - keels of cruciferous crops and powdery scab of potatoes (representatives of the class Plasmodiophoromycetes order Plasmodiophorales).
Representatives Eumycota the vegetative body is a mycelium consisting of thin hyphae (threads) that grow and can branch. Depending on the structural features of the mycelium, they are divided into lower and higher fungi. In the lower mycelium, the mycelium is well developed, but not divided into cells, therefore it is called non-segmented, or unicellular. In higher fungi, it consists of many cells and is called segmented, or multicellular (Fig. 1).
Fig.1. Mycelium types: 1 - in the form of naked plasma in the cell of the host plant; 2 - well developed, but not divided into cells (non-septate); 3 - multicellular.
Depending on the location in the plant, the mycelium can be internal, or endophytic (in most fungi), and superficial, or exophytic (mainly in powdery mildew and some others).
Hyphae of endophytic mycelium are more often located in plant tissues between cells, and only some fungi penetrate directly into cells with their hyphae. In most cases, special outgrowths of various shapes, which are called haustoria, penetrate into cells from the mycelium (Fig. 2). With their help, fungi absorb nutrients from the affected plants, as well as water. 
Fig.2. Forms of haustoria in fungi: 1 - Albugo; 2 - Erysiphe; 3 - Peronospora.
Fungal cells have a nucleus, protoplasm, and almost always a membrane. The nuclei are rounded or slightly elongated, 2-3 microns in size, surrounded by a nuclear membrane. Depending on the type of fungi and the stages of their development, there are from one to several nuclei in one cell.
Protoplasm in young fungal cells usually fills almost the entire cavity, and it contains small vacuoles in the form of rounded vesicles. In older cells, the protoplasm, as a rule, is located in a thin layer near the membrane, the center of the cell is occupied by a large vacuole, through which different directions thin protoplasmic strands.
The cell membrane of most fungi is initially colorless, and with age it often becomes pigmented and thickens.
The mycelium of many fungi can change and take on various forms, the main of which are:
sclerotia- dark solid bodies, consisting of a dense plexus of hyphae with a low water content (up to 10%) and a significant supply of nutrients;
stroma- compacted plexus of the mycelium of the sclerocial type, penetrating the organs of plants. On the surface or inside the affected organs of plants, spore-bearing organs of fungi are formed on the stroma;
chlamydospores- small rounded areas of hyphae, devoid of vegetative mycelium. They contain many nutrients, little water, are often covered with a dense, thickened, sometimes pigmented shell and in most cases are able to tolerate adverse environmental conditions;
gems are formed in the same way as chlamydospores, but differ from them in the instability of forms;
strands- cord-like formations, consisting of parallel placed hyphae, which often grow together.
In some fungi, hyphae of a homogeneous structure are found in strands, in others their differentiation into external ones is observed - thin and strong, internal - wider with unevenly thickened walls;
rhizomorphs- plexuses of mycelium, in which the surface hyphae are dark in color, and the internal ones are light;
mycelial films- dense plexus of mycelium, formed on the surface or inside plant tissues.
Fungi reproduce vegetatively, asexually and sexually. Vegetative reproduction occurs by separate hyphae or mycelium and its modifications, asexual - with the help of special spores formed on special outgrowths of the mycelium. Spores can be of endogenous and exogenous origin.
The first of them are unicellular and are of two types - sporangiospores (fixed), covered with a shell, and zoospores - mobile, with one or two flagella. The receptacles of sporangiospores are called sporangia, and the outgrowths on which they develop are sporangiophores (Fig. 3). Zoospores have zoosporangia and zoosporangiophores, respectively (Fig. 4). 
Fig.3. Organs of asexual reproduction of zygomycete fungi Rhizopus nigricans: 1 - sporangiophores with sporangia; 2 - sporangium (greatly enlarged).
Fig.4. Zoosporangia and zoosporangiophores: 1 - germination of zoosporangium with the formation of zoospores in fungi of the genus Olpidium; 2 - zoosporangium of fungi of the genus Saprolegnia. Zoosporangia on zoosporangiophores of peronosporous fungi: 3 - Python; 4 - Pseudoperonospora; 5 - Phytophthora.
Exogenous spores are formed directly on the surface of special outgrowths and are called conidia, and the outgrowths themselves are called conidiophores (Fig. 5). In some fungi, conidia with conidiophores appear in special receptacles - pycnidia (Fig. 6). 
Fig.5. Conidiokos with conidia in fungi of the genera: 1 - Oedocephalum; 2 - Verticillium; 3 - Sterigmatocystis; 4 - Penicillium; 5 - Erysiplie; 6 - Alternaria.
Fig.6. Pycnidia with pycnospores of fungi of the genus Septoria.
In these cases, conidia are often referred to as pycnospores. Sometimes conidiophores are collected in bundles and then they are called coremia (Fig. 7). In a number of fungi, short conidiophores are formed in a continuous layer with conidia located on a denser plexus of hyphae, the so-called bed (Fig. 8). In mushrooms from the family Tuberculariacea conidiophores with conidia are formed in the form of loose mucous tubercles - sporodochia or the same tubercles, but fused together (pionnots). 
Fig.7. Coremia with conidia of fungi of the genus Sphaerostilbe.
Conidia are unicellular and multicellular, and also differ in shape, color and size.
Sporangiophores are usually unbranched, while zoosporangiophores and conidiophores often have branches with different endings.
Sexual reproduction is carried out by spores, which are formed by the fusion of two heterosexual cells.
In lower fungi, when two motile vegetative zoospores (or gametes) fuse, a zoosporangium, or cyst, is formed. When two cells of different shape and size merge, an oospore appears, and when cells of the same shape merge, a zygospore appears. These spores often have a double coat with various incrustations (Fig. 9).
Higher marsupials reproduce by forming bags with sacspores (ascos with ascospores). In some of them, bags can develop directly on the mycelium, but in most of them they form in special fruiting bodies (plexuses of mycelium hyphae) or on their surfaces.
There are three types of fungal fruiting bodies: cleistothecia, perithecia, and apothecia.
Cleistothecia- closed (closed), more often rounded, with pendants of different shapes. Inside their bags are arranged, as a rule, randomly or in a parallel bundle. The latter are released after the destruction or rupture of the cleistothecia shell (Fig. 10). 
Fig.8. A bed (solid layer) of conidiophores with conidia on a dense plexus of mycelium hyphae in fungi of the genus Gloeosporium.
Fig.9. Oospores and zygospores: 1 - antheridium and oogonium before fertilization and oospore formation; 2 - formed oospore; 3 - sexual process and development of zygospores; 4 - mature zygospore and its germination.
Fig.10. Cleistothecia with asci and sacspores in fungi of different genera of the family Erysiphaceae: 1 - Podosphaera; 2 - Sphaerotheca; 3 - Erysiphe; 4 - Microsphaera; 5 - Trichocladia; 6 - Phyllactinia; 7 - Uncinula; 8 - Leveilluia.
Perithecia- fruiting bodies with a narrow opening at the top (Fig. 11). Bags in them are usually formed in a bunch, and in some mushrooms they are in the plexus of the mycelium, which is called the bag-stroma. Bagostromas resemble perithecia in shape and are often called pseudothecia. 
Fig.11. Perithecia with asci and sacspores of fungi of various genera: Melanomma : 1 - perithecia; 2 Herpotricha : 3 - perithecium; 4 - bag with sacspores and paraphysis; Pleospora : 5 - perithecia; 6 - a bag with bag spores.
Apothecia- open, mostly cup-shaped or saucer-shaped fruiting bodies, on the surface of which bags develop in a wide layer (hymenium), and sterile hyphae - paraphyses are located between them (Fig. 12). 
Fig.12. Apothecia with bags and sacspores in fungi of various genera: Calloria; 1 - apothecia; 2 - a bag with bag spores and paraphyses; Erinella : 3 - apothecia; 4 - bag with bag spores
In higher basidiomycetes, the sexual process ends with the formation of basidia with basidiospores (Fig. 13). Basidia are club-shaped or cylindrical, multi- or unicellular (phragmobasidia). Each basidium usually produces four single-celled, rounded, ovoid or filamentous basidiospores. 
Fig.13. Basidia with basidiospores in fungi: 1 - homobasidial; 2 - heterobasidial; 3 And 4 - teliomentous
All signs of vegetative, asexual and sexual reproduction of fungi are taken into account when classifying them.
In the department Espico1a, pathogens of agricultural crops are represented by three classes of lower (chytridiomycetes, oomycetes, and zygomycetes) and higher (marsupial, basidial, and imperfect) fungi.
Zygomycete class ( Zygomycetes) also includes fungi with a well-developed non-segmented mycelium. During asexual reproduction, they form sporangiospores (in sporangia) or conidia. The sexual process is isogamous (the fusion of two immobile morphologically identical cells) with the formation of a zygospore. Most of these fungi are saprophytes that live on plant debris, but some of them can cause diseases of cultivated plants and insects.
Class marsupials ( Ascomycetes) combines more than 25 thousand fungi with multicellular (septate) mycelium. Many have asexual (conidial) sporulation. Sexual reproduction proceeds with the formation of bags and bag-spores. This class is divided into three subclasses:
fruit marsupials- bags are formed in the fruiting bodies; among them there are many causative agents of diseases of field crops;
cenimarsupials, or loculoascomycetes - bags one by one or more often in groups are formed in the cavities of bag-stromes (pseudothecia); this subclass also contains fungi that cause dangerous diseases in field crops.
Basidial class ( Basidiomycetes) unites about 30 thousand species in which the mycelium is multicellular, and the main organ of sporulation is the basidium, which is formed on the binuclear mycelium as a result of the sexual process. Depending on the type of basidia, this class of fungi is divided into three subclasses: homobasidial(Homobasidiomycetidae - single-celled basidia, club-shaped, with basidiospores located on tops;
heterobasidial (Heterobasidiomycetidae) - multicellular basidia, basidiospores are located one on each cell;
sclerobasidial, or teliomycetes ( Sclerobasidiomycetidae or Teliomycetidae), - basidia are unicellular or multicellular and are always formed from germinating spores, which are currently commonly called teliospores.
Among the latter, smuts are especially harmful, combined in order Ustilaginales, and rust mushrooms out of order Uredinales.
Smut fungi infect various parts of plants, but more often their generative organs. At the same time, the destroyed tissues darken, take on a burnt appearance, from where the name of these diseases came from. Dark-colored teliospores formed in large quantities give the dark color to the affected areas. Previously, they were called chlamydospores, since they are formed by compaction and isolation of the contents of individual cells of the vegetative mycelium and are covered with a thick-walled membrane. However, in smut fungi, such spores do not form a vegetative mycelium during germination, but give rise to a basidium, where the nuclear phase changes.
Rust fungi mainly infect the aerial organs of plants, forming rusty-brown, orange-yellow or dark brown clusters of spores on them, which in most cases protrude through gaps in the epidermis or cortex of the affected organs.
In the development cycle of rust fungi, five types of sporulation have been established, which are usually denoted by the following numbers: 0 - spermogony with spermatozoa; I - aetsia with aetsiospores (aecidia with aetsidospores); II - uredinia with urediniospores (uredopustules with uredospores); III - telia with teliospores (teliopustules with teliospores); IV - basidia with basidiospores.
Each type of sporulation has its own morphological and biological features.
Many causative agents of rust diseases in field crops full cycle their development takes place on two types of plants, therefore they are called dioecious, or heterogeneous. Some of the rust fungi have lost this ability and develop on the same plant, which is why they are called monoecious.
Some species of rust fungi have specialized forms that affect certain plants, as well as physiological races and biotypes that differ in virulence to certain varieties of crops.
Imperfect fungi unite more than 25 thousand species with a well-developed multicellular mycelium, most of which reproduce asexually (conidia) or vegetatively (mycelium). Some of them, under certain environmental conditions, are capable of sexual reproduction of bags with bagospores or basidium with basidiospores.
Imperfect fungi are subdivided into orders according to the type of sporulation (on free or fused conidiophores, in lodges and pycnidia). The structure of the spores, color and number of cells in the spore are also taken into account. Two classifications of imperfect mushrooms are accepted - R. A. Saccardo and A. A. Potebnya, which are used in the atlas.
Bacteria and actinomycetes. Bacteria are unicellular organisms with protoplasmic content. In young cells, the protoplasm is homogeneous; in older cells, vacuoles are found. Bacteria do not have a well-formed nucleus and their nuclear substance is in a diffuse state.
Bacteria come in a variety of shapes: spherical, rod-shaped, spiral, filamentous, and branched. They breed simple division. All bacteria that cause plant diseases are rod-shaped. They are single, connected in pairs or in the form of chains. In some bacteria, the flagella are polar or peritrichous (Fig. 14). For the diagnosis of bacteria, their Gram stain is important: gram-positive - firmly hold the paint and become dark purple, and gram-negative - red. 
Fig.14. Bacteria (under electron microscope): 1 - with polar flagella; 2 - with peritrichous
In addition to morphological characteristics, cultural and physiological characteristics are also of great importance for determining bacteria: the characteristics of growth on nutrient media, the shape and color of colonies, the relationship to molecular oxygen, sources of nitrogen, carbon, and gelatin liquefaction. Often, all these signs are supplemented by data from serological studies (using immunological sera, etc.).
For the final determination of the bacterial pathogen, it is necessary to carry out artificial infection of the host plant and study the symptoms of the disease. Among the bacterial pathogens of field crops, the most common are bacteria from the genera Pseudomonas, Xanthomonas, Aplanobacterium And Corynebacterium.
Actinomycetes, or radiant fungi, occupy an intermediate position between fungi and bacteria. Their vegetative body consists of a thin branched non-septate mycelium, which brings them closer to the lower fungi. However, the nuclear substance in these fungi, like in bacteria, is in a diffuse state. Actinomycetes reproduce by pieces of mycelium and spores, which are formed by segmentation of the spore-bearing branch into separate sections with transverse partitions, or fragmentation - by the breakdown of its contents into separate cells (Fig. 15). 
Fig.15. Types of propagation of actinomycetes: 1 - segmentation; 2 - fragmentation
Actinomycetes cause diseases of beets, potatoes and other crops.
Viruses. Viruses are tiny pathogens that reproduce only in living plant (or animal) cells. Almost all viruses are so small that they pass through bacterial filters, which is why they are often referred to as filterable viruses. There are rod-shaped, filamentous, round, spherical and spiral viruses (Fig. 16). 
Fig.16. Types of viruses (under the electron microscope): 1 - rod-shaped; 2 - filiform; 3 - spherical; 4 - spiral.
Their size is determined in millimicrons (mmm), nanometers (nm), or angstroms (A): 1mmm = 1nm = 10 -9 m, 1A = 10 -10 m.
Each virus of one species has certain characteristics, especially pronounced in their resting forms, which are often called virions, or virospores.
Modern research methods make it possible to isolate viruses from the juice of a diseased plant, purify and obtain them even in crystalline form. The crystalline state of viruses does not reduce their activity. All phytopathogenic viruses are nucleoproteins consisting of a nucleic acid (mainly RNA) and proteins, which include about 20 amino acids interconnected by a peptide bond.
An important feature of viruses is the ability to reproduce their specific structures. Phytopathogenic viruses reproduce very quickly in living cells of susceptible plants or in their isolated tissues growing in artificial nutrient media. They are spread by various insect vectors (aphids and others), as well as during plant grafting or inoculation.
Most phytopathogenic viruses are not very specialized (they infect many plants within botanical families), but some of them infect plants within the same botanical genus.
The classification of viruses is based on the idea of their origin and evolution. Many viruses currently have various synonyms. More often, the generic name of the virus is given from the generic name of the host plant, followed by the word virus, the serial number of its discovery, and the name of the author who first described this virus. For example, the causative agent of winter wheat mosaic is Triticum virus 8 Zazurilo et Sitnicova, Where Triticum- generic name for wheat virus 8- the eighth virus that was detected on wheat, a Zazurilo and Sitnicova- the names of the authors who first described it and proposed such a name.
IN last years in addition to viruses, the so-called viroids, which have an extremely small molecular weight, have been identified. Several diseases of viroid etiology have been described.
Mycoplasma bodies(MPT) as pathogens have recently been found mainly in the phloem, in sieve tubes and plant parenchyma. These are predominantly ellipsoidal or rounded, sometimes elongated or curved, with constrictions, heteromorphic formations (Fig. 17) averaging 200-300 nm in size, occurring singly or crowded. Instead of a shell, they are surrounded only by a double membrane 7–8 nm thick and are very similar in appearance to degenerating mitochondria, as a result of which they could not be detected for a long time. 
Fig.17. Mycoplasma bodies (under electron microscope)
MMT can be propagated and cultivated on complex artificial nutrient media.
All MATs are spread by a carrier (vector). In insect vectors (mainly leafhoppers), they can multiply and accumulate.
Viruses and MPT persist mainly in vegetative plants and insects. Only some of them can be found in seeds, plant debris and soil.
Fig.18. Scheme of the structure of phytonematodes (according to A. A. Paramonov and F. I. Bryushkova, 1956): a - female; b - male; 1 - oral cavity; 2 - body of the esophagus; 3 - middle bulb; 4 - rear bulb with a crusher; 5 - nerve ring; 6 - intestines; 7 - ovary; 8 - oviduct; 9 - uterus (anterior and posterior); 10 - testis; 11 - zone of maturation of spermatozoa; 12 - seed tube; 13 - ejaculatory canal; 14 - spicules; 15 - rudder; 16 - wings of the bursa with ribs.
The body of the nematodes is unsegmented and covered with a smooth or annular cuticle. Their length is from 0.5 to 2 mm, and their diameter is usually about 15-20 microns. In some species, females swell when laying eggs and then their diameter reaches 200-400 microns or more. The nematode consists of a head, body and tail. In the head part there is a nerve or labial ring, in the center of which are the oral cavity and post-labile rings, which vary in shape and are important in the diagnosis of species. The body occupies most of the nematode (from the head to the anus in females and larvae, or to the cloaca in males). The rest (tail) is unequal in shape different types, which is also taken into account when determining them.
In the oral cavity there is a so-called stylet, with which the nematode pierces plant cells. The esophagus consists of a body with a muscular middle bulb, an isthmus covered by a nerve ring, and a posterior (cardiac) glandular part. The enzymes of the glands are partially released into the external environment through the stylet and contribute to the dissolution of the contents of the cells, and the contractions of the bulb help the absorption of food.
Nematodes reproduce sexually with subsequent laying of eggs in a free form (in stem nematodes), in a sticky gelatinous sac (in galls), or eggs accumulate in the body of a female that turns into a cyst (in cyst-forming nematodes).
An indispensable condition for the development of nematodes is high soil moisture. Temperature is also important, but its criteria for different types of nematodes are not the same.
Many nematodes easily tolerate drying and low temperatures.
Soils that are light in texture are a more suitable habitat for most nematodes that feed on plant roots.
Root secretions of some plants stimulate the release of larvae from eggs, while others scare away or even cause their death. This feature should be taken into account when developing protective measures against nematodes. Phytohelminths can be destroyed by predatory nematodes and some fungi.
Known nematodes - carriers of viral, bacterial and fungal plant diseases.
The taxonomy of nematodes as representatives of the animal world is covered in special literature. The most pathogenic species in relation to field crops belong to three families - aphelenchoidids, tylenchids and heteroderids.
When plants are affected by nematodes, germination and plant growth are often slowed down. Affected plants bloom poorly and bear fruit, and often die completely.
