Infectious plant diseases
Infectious plant diseases are caused by viruses. The smallest viruses are so small that they are able to penetrate bacterial filters; for this reason, these viruses are called filter viruses. Viruses can reproduce in living host cells. Viruses are very widespread, and the diseases they cause cause great harm. Unlike fungi and bacteria, viruses are less specialized. One virus can cause disease in many plant species.
Routes of transmission of viruses from one plant to another:
Mechanical damage to the plant and the introduction of infected juice;
Grafting diseased plants onto healthy ones. (Revich, 2007)
Insects such as aphids, cicadas, scale insects and thrips are a source of danger to plants. These insects have a sucking mouthpart; using a stylet, they pierce plant cells and introduce a virus into the plant.
Symptoms of viral diseases vary, some have symptoms of bacterial, fungal and infectious diseases. This leads to diagnostic complications, and then special studies are required. However, diseases caused by viruses are divided into two large groups:
Mosaics;
Jaundice.
Infectious plant diseases caused by bacteria are divided into two classes:
Saprophytic bacteria that live in the soil from which they obtain enough nutrients for their existence. However, under certain conditions, such bacteria can harm plants and cause various diseases in them. This especially applies to weakened and damaged plants. (Uzhegov, 2005)
Infectious plant diseases: dwarfism, jaundice, wilting disease, proliferation, pupation, types of mosaic disease, bacteriosis, fungal diseases and much more.
In control measures to protect plants from infectious diseases, preventive measures are of great importance:
Creating the best conditions for the growth and development of agricultural crops;
Processing of resistant varieties;
Rational seed production;
Chemical seed treatment;
Sprinkling;
Pollination and other plant treatments.
Treatment of infected plants is of great importance, for example, heat treatment of seeds, healing of trees, heating of seedlings, tubers and grafting material that are infected with viruses. When applying quarantine measures, it is possible to prevent the penetration of pathogens from one country to another.
Thus, infectious plant diseases are a whole group of diseases that can be caused by a virus, fungi or pathogenic bacteria.
Fungal diseases are dangerous because they are poorly diagnosed, some of them are difficult to treat and spread very quickly. Often the affected plant must be destroyed. Therefore, it is imperative to use preventive measures. The fungus loves weakened specimens, high temperature and humidity. The source of infection can be soil, dust and newly acquired plants.
The most common fungal diseases are:
Prevention measures
Fungal diseases are easier to prevent than to treat. Therefore, you need to take certain preventive measures when caring for plants:
- Compliance with sanitary standards during work;
- Watering and spraying are carried out using clean water;
- Tools, containers and soil must be disinfected;
- Excessive soil moisture is not allowed;
- Carrying out periodic inspection of plants for the presence of pests;
- Regular ventilation of the room.
Bacterial diseases
The causative agents of bacterial plant diseases are bacteria that penetrate damaged areas of the skin and begin to spread throughout the entire vascular system. Currently, there are no effective treatments for diseases of this type.
Treatment and prevention measures
Bacterial plant diseases are very difficult to treat, and sometimes simply impossible. And transferring them from one plant to another is very easy. Therefore, when carrying out work, you need to constantly disinfect tools and hands. Pots for planting that have been used need to be kept in boiling water for some time.
Treatment of bacterial diseases is possible only at the very beginning of their development. All foci of infection are removed along with some healthy tissue. After this, the remaining parts are sprayed and watered using Bordeaux mixture and other disinfectants containing copper. If this does not help, the plant must be completely destroyed.
Viral diseases
Viral diseases are less common than fungal and bacterial diseases, but they are more dangerous. The routes of infection with the virus can be very diverse: mechanical damage during transplantation, gartering, vaccination; transferring it during work from an infected plant to a healthy one; introduction through pest bites.
Determining the presence of a viral disease is very difficult, since the symptoms are very similar to other plant diseases (withering, rotting, etc.). This can only be done with special tests. All viral diseases are divided into two large groups.
Important! Viral plant diseases completely affect the vascular system, so at the moment there are no treatment methods. Affected plants can only be destroyed.
Diseases caused by improper care
Improper plant care includes primarily:
- Excess or lack of moisture;
- Incorrect content temperature;
- Increased humidity or dry air;
- Excessive or insufficient feeding;
- Wrong light mode.
A characteristic feature of infectious diseases is the spread of the disease (pathogen) from a diseased (infected) plant to a healthy one.
Initial stage disease is an infection that occurs from the moment the phytopathogen penetrates the plant. The period between the introduction of a phytopathogen and the manifestation of plant disease symptoms is called hatchery.
A distinction is made between primary and secondary infection.
Primary An infection is considered to have occurred for the first time among a population of cultivated plants in a specific field during a given growing season. Primary infection occurs from an overwintered infectious beginning. Further spread of the pathogen from a diseased plant to a healthy one is carried out by secondary and subsequent infections
Due to the similarity of many symptoms of diseases that often have different origins, diagnosis (or definition) of diseases based only on external signs is impossible. Used to identify diseasesseveral methods — macroscopic - this is an inspection of plants with the naked eye in a field, garden, etc.;microscopic — using a microscope, the affected tissue is examined; biological, which is based on the isolation of fungi, bacteria, viruses, actinomycetes from diseased plants, isolating them in their pure form and growing them on artificial or natural nutrient media.
Plant diseases - This is a disruption of the normal metabolism of organ cells and the plant as a whole under the influence of a phytopathogen or unfavorable environmental conditions, leading to a decrease in plant productivity or to their complete death.
Phytopathogen– a causative agent of plant diseases, secretes biologically active substances that have a detrimental effect on plant metabolism, affecting the root system, disrupting the supply of nutrients.
Various external signs of plant disease are identified, such as:
To assess the extent of plant diseases, concepts such as epiphytoty and panphytoty
.
In the study of plants, concepts such as epiphytoty and panphytoty are used.
Epiphytoty– spread of infectious plant diseases over large areas over a certain period of time.
Panphytotia– widespread plant diseases covering several countries or continents.
Depending on the origin of the infection, plant epiphytoties are divided into enphytoties and exophytoties.
Enphytotia– a plant disease that arises from a local infectious source that is constantly present in a certain area. An example of enphytoty is infection of rye and wheat with stem rust spores from barberry.
Exophytotics– disease outbreaks caused by infection of non-local origin (carried by wind from outside).
Conditions for the occurrence of epiphytoties
The emergence and course of epiphytoties is possible only under a combination of certain conditions:
- The presence of an infectious onset.
- Plant susceptibility to this disease.
- Timing of primary infection.
- Weather conditions during the growing season.
Phytopathogenic microorganisms spread from reservation areas and infect a large number of plants. As a result of the formation of several generations of the pathogen, new enlarged foci of the disease are created, the area of infection expands, epiphytoty occurs.
Plant susceptibility to the phytopathogen depends on the resistance of the released varieties, time of infection and weather. Depending on the resistance of the varieties, the ability of the pathogen to cause infection, the fertility of the fungus, the speed of development of the pathogen and the harmfulness of the disease change.
The earlier crops are infected, the higher the degree of plant damage and the more significant the yield loss.
Weather factors determining the development of the disease– humidity and air temperature.
The emergence and development of epiphytoty is facilitated by the presence of natural foci of infection in certain areas. Thus, the causative agent of yellow rust of winter wheat persists on certain wild cereals or wheat residues. The intermediate host plant for the causative agent of stem rust of wheat and rye is some species of barberry. In areas where such barberry grows, the infection exists constantly and the development of the disease is potentially possible every year. These types of barberry grow in many regions of the republic.
Crops adjacent to barberry bushes infected with stem rust become infected early; uredospores of the fungus accumulate on them, which are then spread by air currents from the primary source of infection over long distances.
In areas where climatic conditions best meet the requirements of the fungus, epiphytotics of the disease occur within 1-3 years.
The most dangerous plant diseases are:
- Late blight of potatoes is a shortfall in yield due to the death of tops during the formation of tubers, as well as their massive rotting in the ground. Observed in the second half of summer. Crop losses range from 15% or more.
- Cereal rust is a fungal disease that destroys the crop by 50 to 100%.
Plant pests - Colorado potato beetle, locust, meadow moth, etc.
– it is necessary to ensure that the disease does not spread throughout the garden. In order for control measures to be truly effective, you need to know exactly what is wrong with the crop.
It should be remembered that it is easier to prevent a disease than to treat it. The most reliable way to combat plant diseases is a high level of agricultural technology and the use of healthy planting material. Plants must receive sufficient quantities of nutrients, water, and sunlight, in which case they will be able to resist pests and diseases. The main types of plant diseases are fungal, viral and bacterial. A separate group of non-infectious plant diseases associated with a deficiency of certain substances has also been identified.
You can find a description of plant diseases, as well as the most effective control and preventive measures on this page.
Fungal plant diseases, means and methods of combating them
The most common fungal plant diseases are the following.
Fusarium. This disease causes the greatest harm to gladioli, daffodils, tulips and other bulbous plants, as well as irises and dahlias. Mushrooms live in the arable layer of soil and through the root system enter the bulbs, stems, leaves, buds, and seeds. In affected plants, the root system develops poorly; the leaves are long, thin, curved, and gradually turn yellow, starting from the tips. Bulbous plants are easily pulled out of the soil. Often the disease occurs with mild symptoms, which is especially dangerous.
If the bottom is slightly damaged, the bulbs do not differ in appearance from healthy ones, so they can be planted in the ground. The leaves of the affected plant remain green for a long time, but when dug up, it is discovered that most of the roots have died, and red-brown spots are visible on the bulb itself; small whitish spores of the fungus can be discerned at the bottom. A pinkish-white coating in the form of a web appears between the scales. When storing affected bulbs, the fungal infection continues to develop intensively, penetrating the entire bulb and causing its death. At low humidity, the bulbs dry out, and at high humidity and temperature, soft rot forms. The development of fusarium is facilitated by excess humidity or, on the contrary, drought, dense plantings, heavy soils, excess organic matter, and the presence of mechanical damage to the bulbs. The pathogen persists in soil, plant debris, and planting material.
Coping with fusarium is not easy, as it is often asymptomatic. Therefore, the main importance is the prevention of plant diseases and, above all, timely digging of bulbs. They must be dried quickly and stored in a ventilated area. To protect plants from this disease, before planting, planting material is kept for 30 minutes in a 0.2% suspension of foundationazole. All plants suspected of the disease should be destroyed. There are no varieties that are immune to fusarium, but the degree of resistance may vary. If the disease appears annually, susceptible varieties should be excluded from the collection. For the purpose of prevention, crop rotation is used, alternating plantings with resistant plants (salvia, calendula, eschscholzia, marigold).
An effective method of combating this plant disease is treatment with thiazone. The drug is mixed with sand (1:1) and applied in the fall or spring a month before planting, then dug onto the bayonet of a shovel and watered the area.
Gray mold, or botrytis. This is one of the main plant diseases; it affects many flower crops - tulips, irises, peonies, gladioli, lilies, roses, chrysanthemums, asters, gillyflowers, carnations. The fungus can damage all plant organs throughout the growing season. Shoots, seedlings, flowering plants, bulbs, tubers, and rhizomes become diseased. Planting material may be affected during storage.
The disease is caused by two types of fungus. The first affects the stems and ends of leaves at high humidity. The leaves become discolored, then turn brown and rot, becoming covered with a gray coating. The second type of fungus causes dry rot of rhizomes, bulbs, and tubers. The development of diseased plants slows down. Rot can also spread to the bases of the leaves, where a gray coating of fungal spores forms. At the same time, the fan of leaves of gladioli and irises falls.
The development of the disease is promoted by high humidity, dense plantings, excess nitrogen, heavy clay soils, mechanical damage to the bulbs and freezing of the rhizomes. Intensive development occurs during cool and humid summers. The causative agent of the disease is transmitted through contaminated soil and plant debris, as well as affected planting material.
When combating this plant disease during the growing season, it is important to avoid excessive application of nitrogen fertilizers. When signs of damage appear, spray with 0.2% foundationazole or 1% Bordeaux mixture once every 10 days. Severely affected specimens are discarded. Healthy planting material is stored for storage, good ventilation and the required air temperature are provided in the storage. During storage, affected tubers or bulbs are discarded and destroyed.
Sclerotial rot. The disease affects bulbous plants, most often tulips, hyacinths, and daffodils, both during the growing season and during storage. In the spring, infected bulbs do not germinate or produce yellow, twisted shoots.
As you can see in the photo, with this plant disease, a white coating resembling cotton wool forms on the bulbs, with dark dots of fungal spores:
Photo gallery
With severe damage, the planting material softens and rots. The disease may appear as a sunken rot spot with a dark border in the upper part of the bulb. The infection is transmitted through the soil and affected planting material.
The main measure to combat this plant disease is to cull diseased crops and bulbs, destroy plant residues, and, if necessary, treat with fungicides.
Penicillosis, or green mold. The disease affects the bulbs of tulips, daffodils, hyacinths, and gladioli during the dormant period as a result of mechanical damage during harvesting and cleaning, as well as poor storage conditions. Poorly dried, heavily chilled and mechanically damaged bulbs are affected. The disease often occurs as a secondary disease due to gray mold and fusarium. Small light brown spots appear on the bottom and around it, which can spread not only along the surface, but also deep into the bulb. Infected planting material either completely rots or produces stunted seedlings. Yellow-brown spots with an abundant bluish-green coating of fungus form on the leaves.
It is necessary to observe the temperature regime when storing the bulbs, ensuring sufficient ventilation. Affected planting material is rejected both during storage and before planting. You should try to avoid mechanical damage to the bulbs. A good way to combat this plant disease is to treat the planting material with a 0.2% solution of foundationazole for 30 minutes.
Leaf spot. A dangerous disease caused by various types of fungi. Pansies, primroses, irises, phlox, poppies, bearded carnations, delphiniums, dahlias, and roses may be affected. Spots of various colors, shapes and sizes appear on the leaves. Affected leaves dry out over time. appears in the second half of summer. Warm, humid weather promotes the spread of the disease. Since the affected leaves serve as the reservoir of infection, an important point in the fight against this disease is the destruction of plant debris and dried leaves.
Effective drugs to combat this plant disease are copper- and zinc-containing fungicides.
Bacterial plant diseases and methods of protection
Wet rot. This is a bacterial plant disease that affects bulbs (daffodils, tulips, hyacinths), and is also one of the most dangerous diseases of irises. This type of plant disease is manifested by yellowing and wilting of leaves, stunted growth, bulbs and rhizomes soften, become covered with mucus, and emit a sharp, unpleasant odor.
The diseased plant dies. The development of the disease is facilitated by excess nitrogen in the soil, lack of calcium and phosphorus, application of fresh manure, high humidity, and dense plantings. The disease is transmitted through bacteriosis-contaminated soil and plant debris. The infection can penetrate plants through damage caused by insects (larvae of beetles and hoverflies, wireworms). In irises, the spread of rot is facilitated by freezing of the rhizomes.
To protect plants from this bacterial disease, diseased crops and bulbs are discarded. Before planting, rhizomes and bulbs are kept in a 0.5% solution of potassium permanganate for 30 minutes or in a suspension of captan (0.2-0.5%) for an hour.
All types of viral plant diseases manifest themselves with a number of characteristic symptoms. The leaves turn yellow, become covered with necrotic spots and bizarre patterns in the form of a mosaic, stripes, and strokes. The leaves become wrinkled and deformed (wrinkled, curled, narrow-leaved). Greenish-brown stripes may appear on the stems, and their growth slows down sharply. The disease spreads through equipment and even the gardener’s hands; infection can be transmitted by sucking insects, such as aphids.
With a lack of iron, magnesium, other trace elements, as well as damage by harmful insects, similar symptoms may be observed. If after feeding with microelements the symptoms of the disease do not disappear, then there is a high probability of infection by viruses.
There is no cure for viral diseases. The only recommendation for combating this plant disease is to dig up the diseased crop and burn it, and disinfect the soil with a dark crimson solution of potassium permanganate. You should also combat vectors of infection and disinfect tools and hands after contact with diseased plants.
Mosaic. Almost all ornamental crops are susceptible to this disease. This plant disease got its name because when infected with a virus, a pattern in the form of a grid or yellow stripes, reminiscent of a mosaic, is formed on the leaves. Plant growth slows down, shortened peduncles are formed, flowers are underdeveloped and deformed. Flower petals become variegated. Numerous side shoots may form, resulting in excessive bushiness. Bulbs ripen ahead of schedule, but the bulbs are small and defective. The pathogen persists in infected plants and soil. The mosaic virus is transmitted by sucking insects -,.
Variegation. This viral plant disease causes veins or spots of uncharacteristic color to appear on the petals. Tulips most often suffer from this, but the disease can also occur in dahlias, chrysanthemums, lilies, and violets. A white or yellow feathery pattern appears on the petals of light red, pink, and lilac tulips. In dark red and purple varieties, the color of the buds becomes less saturated, and dark streaks appear on them. Many tulips in which the disease is mild can survive for years and be a source of disease all this time. The flowers and bulbs of such plants gradually become smaller, and ultimately they degenerate.
Non-infectious plant diseases, methods of control and prevention
Diseases of flower crops can be caused not only by infection by infectious agents, but also by improper care, poor soils or planting material, lack or excess of nutrients, unfavorable weather conditions, too frequent treatments with pesticides, and air pollution.
An imbalance of nutrients in the soil adversely affects the development of plants. Thus, with a lack of nitrogen, the leaves turn pale and the number of flowers in the inflorescence decreases. Excess nitrogen is also undesirable, especially in combination with a deficiency of potassium and calcium: the stems lose strength, the flowers in the upper part of the inflorescence are underdeveloped, the development of bulbs is disrupted, and plants are easily affected by fusarium.
Leaf chlorosis. This anomaly is caused by a lack of microelements (most often magnesium). A high lime or potassium content in the soil can cause magnesium to be difficult for the plant to absorb. The tissues become pale or yellowish-green, but the veins remain bright green. The color of the entire plant or part of the leaves changes. Chlorosis is often observed in cold springs, more often on thin sandy and sandy loam soils. Perhaps the anomaly develops in plants weakened by other diseases. To prevent this non-infectious plant disease, plants are sprayed four times before flowering with a solution of magnesium sulfate.
Withering. The disease begins at the tips of the shoots and slowly spreads downwards. Weakened plants are usually affected. Very often, wilting occurs when there is a deficiency of potassium, calcium, phosphorus and boron in the soil. The occurrence of the disease is facilitated by freezing of shoots, diseases or leaf spots.
Non-infectious diseases quite often affect tulips.
Drying flowers. The disease affects the flower primordium of tulips. If this process occurs before planting the bulb, then the remains of the flower primordium in the developed plant can be found in the form of a small membranous feather between the leaves. Such plants have shortened stems and smaller leaves. The dead parts of the flower never rot or become moldy, as with gray rot. With weak development of the disease, only the stamens are damaged.
Drying of a flower bud in a bulb may be due to too high a temperature late in storage. This is usually observed when transporting bulbs (transit heating). After planting, drying of flowers is often observed in very fast growing varieties and with poor development of the root system. This is also facilitated by prolonged cooling or high temperature in greenhouses during forcing. The time at which the bulbs prepare for forcing begins to cool is also important.
The main method of preventing this non-infectious plant disease is compliance with the optimal storage regime for planting material. To prevent the flowers from drying out, the bulbs should be stored at a temperature of 20 °C or slightly higher after harvesting. Overheating of planting material during transportation should be avoided. When forcing in boxes, the temperature after transferring the tulips to the greenhouse should not exceed 18-20 °C. If the cooling was very long or rapid growth is expected during late forcing, it is necessary to maintain a temperature of 15-16 ° C.
What other non-infectious plant diseases are there and how to deal with them
Below we describe what other non-infectious plant diseases there are and how to deal with them in your garden.
"Resin". On the fleshy scales of the bulb, bubbles appear, filled first with light, and then with light yellow or brown viscous liquid, which can protrude out through cracks. Gradually it hardens and turns into a resin-like substance, localized under the surface layers of the scales. Such bulbs usually develop normally after planting. “Resin” can form if the planting material has been subjected to slight mechanical damage (for example, during sorting) or exposure to ethylene.
Varieties prone to “resin” formation should be dug up and processed very carefully; Under no circumstances should they be stored with other onions that emit ethylene.
"Swan Necks". This anomaly can occur both in open ground and in greenhouses, especially during late forcing. The sprout has a double curl, develops sluggishly or does not grow at all. In some varieties, the anomaly repeats from year to year. Apparently, it occurs when the scales dry out strongly or the top of the bulb is damaged.
Leaf variegation. Manifestations of the disease are different. Sometimes a yellow or silvery border appears on the leaf blades. This may be a consequence of mutations. This is often regarded by gardeners as a viral disease, and the plants are destroyed. Or pale yellow or greenish-yellow stripes appear on the leaves. Often an anomaly appears in one batch of tulips and disappears the next year. Yellow spots on seedlings and unfolded leaves form if the bulbs are planted in herbicide-treated soil.
Degenerations (growth abnormalities) are observed both in the above-ground parts of plants and in bulbs.
The most common are stepsons and “horse teeth”. In the first case, in addition to the usual leaves, several small ones develop from the baby. The main leaves are long, sharp, with slightly curved edges. Such plants bloom later, and small bulbs may not produce flowers at all. Tulips with such a growth anomaly go unnoticed for a long time.
Sometimes the rudiment of the bulb in the axil of the scales splits, and elongated, flattened and angular bulbs appear tightly adjacent to each other. They sit in one row and resemble a horse's jaw. This degeneration is inherited.
In some bulbs, the scales are formed unevenly. They close together at the top and form concentrically arranged “teeth”, reminiscent of an artichoke.
The main method of protecting plants from this disease is timely detection and careful removal of tulips with signs of degeneration.
Chemical protection and control of plant diseases using drugs
To protect plants from diseases, a comprehensive system of measures is necessary. A special place is given to prevention. Cultural circulation is of utmost importance. In place of dug up perennials and bulbous plants, it is useful to place annuals that produce phytoncides (nasturtium, mustard, calendula, marigolds) and plow them in in the fall. At the same time, there is a noticeable improvement in the soil from the pathogens of fusarium and gray rot. Perennials are usually returned to their old place after 4-6 years.
How to deal with plant diseases if it is not possible to alternate crops? In this case, the soil is treated with nitrafen, which has a fungicidal, bactericidal and partly herbicidal effect. In autumn, the soil is dug up to a depth of 20-25 cm and watered from a garden watering can with a sprayer with a solution of nitrafen (250 g per 20 liters of water per 1 m2). You can also use such preparations to protect plants from diseases such as copper oxychloride (0.4%), basezol (0.2%) and topsin (0.1%) for treating the soil.
You should use only healthy planting material, avoid thickening the plantings, periodically cull and destroy diseased plants, and disinfect the soil in the holes. It is important to apply organic and mineral fertilizers in optimal doses.
The addition of microelements contributes to the health of plants. Often this alone is enough to prevent many diseases. Spray with a solution of microelements 2-3 times per season. To do this, take 50 g of sulfuric acid, 50 g of iron and copper sulfate, 10 g of boric acid and 10 g of cobalt nitrate per 10 liters of water.
Most of the necessary nutrients and microelements are contained in the so-called “green manure”. Fertilizing with infusion of nettle, comfrey, tansy, horsetail, and marigold helps strengthen plants and increase their resistance to disease. In addition to nutritional properties, such solutions also have an insecticidal effect, which manifests itself in improving the health of the soil and protecting plants from harmful insects and pathogenic fungi.
Disinfection of racks, trays, boxes and work equipment, and storage rooms is of great importance. General cleaning and wet disinfection are carried out annually at the end of the growing season. Use formaldehyde (4%), copper (5%) or iron sulfate (8%) and bleach solution (400 g per 12 liters of water - prepared 2-4 hours before use).
For chemical protection of plants from diseases, it is better to use a copper-soap preparation (200 g of potassium green soap and 20 g of copper sulfate per 10 liters of water), foundationol (0.2%), copper oxychloride (0.4%), karbofos (0.2 %). The simplest household alkaline chemicals are highly effective against fungal diseases - drinking and soda ash, potash, ash (especially sunflower). The concentration of the solution of these substances is 0.5-1%. In addition, alkaline chemicals contain nutrients necessary for plants, so they can also serve as fertilizer. Alkali solutions are harmless to others. After heavy rains, which bring a lot of spores of all types of pathogenic fungi, as well as during heavy dew, it is recommended to systematically spray the plants with solutions of household alkaline chemicals.
When storing planting material, it is necessary to maintain temperature conditions and maintain optimal air humidity. Specimens suspicious for diseases are periodically inspected and discarded. Before planting, the bulbs are treated with fungicides and a solution of potassium permanganate.