infectious disease of the ear, causing significant crop losses, making grain unsuitable for use for food and feed purposes

Specialists from the Crop Science division of Bayer, together with the laboratory of mycology and phytopathology of the All-Russian Research Institute of Plant Protection, have prepared unique information about dangerous disease- fusarium head blight; its biology; symptoms; factors that increase the risk of its occurrence; diagnostic methods, as well as control measures that allow obtaining high yields of high-quality grain

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Fusarium is a dangerous and very common disease of plants at any age, caused by fungi of the genus Fusarium

The pathogen, at various periods of plant development, can infect roots, leaves and ears.

Some types of fungi form mycotoxins (from the Greek mukos - mushroom + toxikos - poison) - molecules associated with the secondary metabolism of fungi, which exhibit toxic properties and make it unsuitable for use for food and feed purposes.

Toxins cannot be detected without special equipment, and they can be found not only in grain, but also in its processed products - flour and bread.

Symptoms

Infection of plants with fusarium leads to both a decrease in yield and a catastrophic deterioration in its quality.

Symptoms of fusarium head blight:

1. pink-orange coating of mycelium and sporulation of the fungus on the glumes of the ear;
2. pale pink sporulation of the fungus on the glumes;
3. eye spot on glumes;

With mild damage, the mycelium is located in the grain shells, while visually the grain is practically no different from healthy ones. But with more pronounced damage, the pathogen penetrates deeper, reaching the aleurone layer and the grain germ. Diseased grains are usually lightweight. Their surface is deformed (“wrinkled”), with a depressed deep groove and pointed barrels, and may have a pinkish tint.

Symptoms of grain fusarium:

• The affected grains are puny, wrinkled with a depressed deep groove and pointed barrels;
• The surface of the grain is discolored or pinkish, without shine;
• The endosperm is loose and crumbly; low glassiness of the grain or its complete loss;
• In the groove and especially in the embryonic part of the grain there is a cobweb-like coating of fungal mycelium, white or Pink colour and accumulations of conidia, in the form of pads;
• The grain germ is nonviable, dark in color on the cut.

However, apparently healthy grain can also be affected by fungi and contain mycotoxins!
This disease can cause damage to a batch of healthy and apparently healthy seeds. The presence of a milligram of mycotoxins in a kilogram of grain destroys all its beneficial properties.

Causes

Infection of leaves and ears with fusarium occurs by ascospores formed in fruiting bodies on post-harvest residues, or by conidia that appear on stubble residues or on the lower infected leaves. Infection of the ear mainly occurs during wheat flowering in conditions of sufficient humidity and at temperatures above +20°C. This subsequently leads to infection of developing grains.

The primary lesion occurs on the lower tiers of dead leaves. However, in most cases, no specific symptoms not noticeable. The resulting spores are spread by splashing rain.

The main period of infection is the flowering time of cereals. In this case, the anthers apparently serve as the entrance gate to each individual flower. Nutrient-rich pollen promotes the germination of fungal spores. Any weakening of the plant contributes to the defeat of the ears by fusarium.

Microscopic development

1. Conidia develop on the surface of the plant

2. Form mycelium

3. Penetrate the plant

4. Develop in tissues

5. After the incubation period, new conidia are formed

Factors influencing Fusarium infection

Plants of cereal crops are susceptible to fusarium in the flowering phase at high humidity and temperatures of about +20-25°C (especially F. graminearum). But for species such as Fusarium sporotrichioide and F. poae high humidity and air temperature are not mandatory conditions infection. Weather conditions are an important, but far from the only factor influencing the development of the disease.

Tillage

• Tillage methods have a great influence on the development of fusarium.
• The presence of fungal-infected plant residues on the surface or in the surface layers of the soil after minimal tillage greatly increases the likelihood of infection of growing plants.
• This means you can reduce the risk of infection by plowing plant debris into the soil, where it decomposes more quickly.

3000 2000 1000 0

Crop rotations

• The rotation of crops in a crop rotation has a particular impact on the potential development of infection.
• Saturation of crop rotation with grain crops promotes the accumulation of inoculum.
• Low-field crop rotation, especially including corn, increases the risk of plants being damaged by Fusarium.
• Beetroot is also an unfavorable predecessor.

1500 1000 500 0 DON content, µg/kg

Variety resistance

• Cultivation of resistant varieties has a greater impact on reducing disease incidence and improving grain quality.
• Most cultivated varieties of grain crops are susceptible to fusarium.
• Bread wheat varieties vary in level of susceptibility from relatively resistant to highly susceptible.
• Durum wheat and oats are highly susceptible to fusarium grain blight.

These data are taken from studies on the level of deoxynivalenol DON, a minotoxin secreted by fungi of the genus Fusarium. France 2000 - 2001, number of fields 663 pcs.

Find out in 30 seconds how the Fusarium pathogen develops

The gene modified with green fluorescent protein makes it possible to monitor the development of the fungus Fusarium graminearum in the ear.

Under favorable conditions, fusarium completely infects the ear in 5-6 days!

Consequences

Mycotoxins (from the Greek mukos - mushroom + toxikos - poison) are specific toxic substances produced by fungi. Poisonous macromycetes, such as toadstool and red fly agaric, are well-known “poisoning villains”. But their microscopic relatives (micromycetes) are no less poisonous and even more dangerous. After all, their toxins cannot be detected without special equipment, and they can be found not only in grain, but also in its processed products - flour and bread.

What are mycotoxins?

• Mycotoxins are molecules associated with secondary metabolism mushrooms that exhibit toxic properties to humans and animals.
• All major fungal species that cause Fusarium blight can produce mycotoxins.
• Mycotoxins produced by various types of fungi. Fusarium have various toxicological properties.
• Mycotoxins have different effects on different types, such as pigs, poultry, people, etc.
• The most common mycotoxins in cereals are deoxynivalenol (DON) and T-2 toxin

Toxic effects

Trichothecenes

type A(T-2, HT-2, DAS)

F.sporotrichioides F.langsethiae

• The most toxic metabolites.
• Responsible for nutritional toxic aleukia (ATA)
• Causes epidermal necrosis and ulcerative stomatitis, serious gastrointestinal disorders that can lead to death

type B(DON, NIV)

F.graminearum F.poae F.culmorum F.cerealis

• Acute toxicity characterized by vomiting (more sensitive in pigs), food refusal, weight loss, diarrhea, tissue necrosis
• No indication of carcinogenic, mutagenic or teratogenic effects

Zearalenone

F.graminearum F.culmorum

• Reduce animal productivity
• Estrogenic effects causing infertility, miscarriage (pigs are especially sensitive)
• Possible effect on cervical cancer in women

Fumonisins

F.verticillioides F.proliferatum

• Equine leukoencephalomalacia (a disease of horses), characterized by neurotoxic effects, pulmonary and cerebral edema, and liver damage
• Possible link to esophageal cancer in humans

Moniliformin

F.tricinctum F.avenaceum

• Changes in cardiac muscle tissue
• Intestinal bleeding (limited studies)

Distribution of deoxynivaleonol in fusarium wheat milling products

It has been proven that in bread made from fusarium grain the content of mycotoxins does not decrease, and sometimes even increases, especially when producing yeast dough and bread!

Fusarium
threat to people!

Effect of mycotoxins on animals

Wheat represents 50% of pig growth feed. If mycotoxins are present, feed consumption by pigs is significantly reduced. Serious symptoms include refusal to eat, weight loss and vomiting. Moreover, reproductive function may be affected

Impact of fusariotoxins contained in feed on the health of animals and poultry

• Refusal to feed
• Decrease in productivity
• Immunosuppression
• Ulcerative stomatitis
• Epidermal necrosis
• Damage to internal organs (liver, kidneys, reproductive system organs, etc.)

LD50 indicator for mycotoxins entering through the gastrointestinal tract

LD50- the average dose of a substance that causes the death of half the members of the test group. ZhM- live weight
Relative toxicity- degree of toxicity of a substance in comparison with another substance (in in this case compared to T-2 toxin). more toxic substance< 1,0 < менее токсичное вещество

The ability of fungi of the genus Fusarium to cause typical symptoms and produce species-specific mycotoxin

T-2 and HT-2 toxins are among the most dangerous mycotoxins produced by fungi of the genus Fusarium. At the same time, their producers - F. langsethiae and F. sporotrichioides - can develop on the ear without visible signs.

T-2 toxins
hidden threat

Occurrence of species of the genus Fusarium in grain samples from various regions of Russia

Infection of winter wheat grain with fungi of the genus Fusarium depending on its predecessors

The least favorable predecessor in terms of the subsequent risk of developing fusarium is corn. The presence of such a precursor makes it necessary to develop a strategy for protecting winter wheat from fusarium head blight.

HOW TO DETERMINE FUSARIOSIS?

1. Visual assessment

In areas where the species F.graminearum, F.culmorum, and F.avenaceum are distributed, visible symptoms of fusarium blight on ears can be detected in the field. Infection with fusarium does not always manifest itself visually, but this disease can cause the “disqualification” of a batch of full-bodied and apparently healthy seeds. The presence of literally a milligram of mycotoxins in a kilogram of grain - and that’s it! IN best case scenario such grain will be used as fodder. Neither protein content, nor IDC indicators, nor nature matter if the grain contains a microscopic amount of a deadly poison of fungal origin.

• Fast and inexpensive way

The chain reaction is a process that occurs in three stages (denaturation, annealing and expansion), repeated in several cycles.
At each stage of the process, the number of copies doubles from two to four, then to eight, and so on. After 20 cycles there are approximately 1 million copies, that is, enough material to determine the desired DNA using the traditional method. Advantages:
• PCR is a relatively fast and reliable method for identifying fungi.
• Allows you to detect the presence of a certain type or several types of fungi in plant tissue. Detection of the number of fungi is possible using quantitative PCR (real-time PCR).
• The amount of fungal DNA detected is related to the presence of mycotoxins they produce.
Flaws:



4. Planar waveguide technology

Reliable and quick method, using innovative technology planar waveguide to detect four to five toxins in one measurement.

Advantages:
• Simultaneous determination of several mycotoxins.
• Ease of sample preparation
• Quick result (25 min)
• No special laboratory training required
Flaws:
• Need for specialized equipment



How to fight fusarium?

For more than 20 years, Bayer has worked on the problem of fusarium blight, a worldwide disease that affects a variety of grain crops.

Intensive research has led to a better understanding of disease aspects and the development of optimal solutions to suppress and reduce pathogenic fungi negative impact on the quality of the product.

Application of fungicides

Treating crops with a fungicide during flowering is an important method of combating fusarium.

Azoles have fungistatic effect. They suppress the synthesis of ergosterol in the fungal cell membrane at the level of formation of dimethylergostatrienol from lanosterol by inhibiting the cytochrome P450-dependent reaction of C14-a-dimethylation

Azoles are the best weapon! against fusarium

Bayer's Crop Science division has developed a new active ingredient, prothioconazole, which provides high level protection of the ear from fusarium and, as a result, leads to the most effective reduction of the level of mycotoxins in the grain.

According to independent assessment(information from the website www.eurowheat.org) combination of various active ingredients in the fight against fusarium head blight in European countries tebuconazole with prothioconazole has maximum effectiveness against fusarium head blight!

Both active substances belong to the group of triazoles and inhibit the biosynthesis of sterols, disrupting the integrity of the cell walls of pathogens.

Significant amounts of precipitation combined with moderate temperatures in May and early June contributed to the significant development of wheat diseases, and ear diseases in particular. It is known that the physiological role of the ear in the formation of the future harvest is second only to the flag leaf and, according to various sources, amounts to 20-25%. Therefore, protecting the ear from diseases is crucial for obtaining a high and high-quality wheat grain yield.

Wheat ear diseases: danger to the crop

Particular attention should be paid to the monitoring and control of fusarium - a disease of the wheat ear, which had epiphytotic development in 2014, and therefore a significant supply of infection, despite its insignificant manifestation last year. The species composition of wheat ear pathogens largely depends on the phase of plant development, genotype and agricultural technology of the variety, temperature and air humidity, and therefore differs from year to year.

Fusarium head blight of wheat

Fusarium head blight disease in wheat manifests itself in the heading phase and develops before harvesting. The affected ear acquires a light color (discolored) at the base, from its central part or from the top. Only individual spikelets can also be affected - then they acquire a light yellow color and are clearly visible against the background of the rest of the green ones (photo 1). The causative agents of the disease are fungi of the genus Fusarium.

Mycelium and conidial sporulation of Fusarium spp can be found on the affected glumes. in the form of purple pads.

The entry of pathogens into the central rachis is blocked by nutrients to all spikelets located above. This leads to full grain (or empty grain).

Infection of plants occurs mainly during flowering, when the ascospores of pathogens mature. Wheat anthers is good nutrient substrate for the growth of fungi of the genus Fusarium, in particular F. graminearum. Fungal hyphae colonize anther tissue, penetrate the embryo and spread through the grain shell.

It is believed that the degree of disease development depends 70% on the variety and agricultural technology, and 30% on weather conditions. The intensive development of fusarium head blight is promoted by a temperature of 20 ... 25 ° C and high air humidity (75% or more) during the period from flowering to harvesting.

Diagnosis of fusarium head blight in wheat

In turn, the degree of damage to grain depends on the type of pathogen and the time of its penetration into the tissue. In this regard, two types of wheat ear damage by the disease are distinguished:

1. A pronounced (deep) fusarium grain, according to surface (macroscopic) analysis, is distinguished by plus-leaf and pink color due to the presence of fungal mycelium. This form of damage occurs due to early infection of ears of corn in the field (in the flowering phase) mainly by the fungi F. culmorum, F. graminearum and F. avenaceum.
2. The hidden (superficial) form of Fusarium grain occurs when it is damaged late, has a weak infectious load, or is damaged during harvesting and storage. Such grain is no different from healthy grain, but is a source of infection during storage and sowing.

When analyzing grain, it is necessary to distinguish between fusarium, discolored and pink-colored (non-fusarium) grains. The main features characterizing fusarium grains are:

• the grain is whitish, chalky, with a complete loss of shine; on individual grains there are spots of pink-raspberry or creamy pink color;
• the endosperm is fragile, with a mealy consistency; for late damage by fusarium - from mealy to partially glassy;
• most grains are wrinkled, flat, have pointed sides and a well-pressed groove; in the case of late damage by fusarium - the shape of the grooves and grain size are close to normal, sometimes swollen, with peeling shells;
• the embryo is not viable and is black when cut; there is fungal mycelium on the embryo and in the groove.

Discolored and pink-colored grains differ from fusarium grains in their fullness, normal endosperm and glassiness, a viable pale yellow (on cut) embryo without fungal mycelium. Pink-colored grains have a normal shine and spots of pink-red shades (mainly in the embryo), and do not stain.

Damage to the ear leads to infection of the grain, as a result of which the yield shortfall reaches 45-73%, the sowing quality of the seeds deteriorates: germination energy and germination can decrease by 24%, the weight of 1000 seeds - by 39-72%. The barrenness of affected plants sometimes reaches 60%. Laboratory germination of seeds from an ear with obvious signs of fusarium can be reduced by 96%. The density of gluten and the baking properties of flour deteriorate, the amount of protein decreases by 1.3-5.6% with the release of ammonia, and dangerous toxic substances (fusariotoxins) accumulate in the grain. When Fusarium grain is used for food or feed purposes, it can cause poisoning of people and animals.

The most common fusariotoxins that contaminate agricultural products are T-2 toxin, deoxynivalenol (DON, vomitoxin) and zearalenone (F-2-toxin). DON is most often released, and T-2 toxin is considered the most dangerous.

In grains with clear visible signs of fusarium blight, the mycelium of fungi of the genus Fusarium penetrates all tissues - the shell, aleurone layer and endosperm. The main location of the mycelium of Fusarium spp. in grain with latent infection - pericarp cells. Deformation and disruption of the density of its transverse cells occurs. The thickness of the cells of the outer epidermis increases by 1.5-2.0 times compared to unaffected ones, and the cells of the walls of the aleurone layer become thinner by 2.0-2.5 times.

The main sources of Fusarium infection in wheat are affected plant residues and seeds.

Septoria head blight of wheat

Wheat ear disease manifests itself on the leaves, stem and ear of wheat. Typical signs of septoria leaf blight are the appearance of first light, yellow, light brown, and sometimes faint spots with or without a dark border. Black small pycnidia are located in the center of the spot or on its entire surface. Affected leaves often dry out. The spots on the stem are vague, without a clear border.

On the glumes, septoria appears as dark brown spots, sometimes with a purple tint (photo 2). In affected areas, the tissue may become lighter in color and pycnidia may appear on it.

Diagnostic signs of septoria ear blight in wheat depend on the resistance of the variety, weather and agrotechnical conditions.

The massive development of septoria is promoted by a temperature of 20 ... 25 ° C, the presence of drip moisture or a relative air humidity of 90-100%. Under such conditions, pycnospores can germinate within several hours after emerging from the pycnidia. Dry periods of the growing season significantly suppress the development of the disease.

The grain in the affected ear becomes flat or completely absent. Underdevelopment of the ear leads to yield losses of 20-30% or more. Technological indicators of grain quality are significantly deteriorating.

Septoria infection persists on plant residues and wheat seeds, carrion seedlings, winter crops in the form of pycnidia and mycelium. Wild grains can also be a source of infection.

Olive mold on wheat stalks

Wheat ear disease manifests itself in wet weather during the ripening period on stems, physiologically aging leaves, ears and grains in the form of an olive-black velvety coating - mycelium and conidial sporulation of the causative agent of the disease (photo 3). After compaction, the plaque takes on the appearance of turf.

With frequent rains, spikelets affected by fusarium are also colonized by the olive mold pathogen.

When harvesting wheat is late and in rainy weather conditions, olive mold quickly spreads, causing blackening of the entire ground mass of plants. The development of the disease is enhanced by the presence of “honeydew” on the spikelets due to the high number of cereal aphids or the development of the pathogen (Claviceps purpurea (Fr.) Tul.). The crop shortfall can reach 10% or more. The affected grain is flat and has reduced germination.

The main source of infection of wheat ear disease is affected plant residues and seeds, where the fungus persists in the form of mycelium and conidia.

Wheat smut

The first signs of wheat ear smut disease clearly appear starting from the milky ripeness phase of the grain. At this time, the affected spikelets are somewhat splayed, with a blue-green color. When the affected grain is crushed, a grayish liquid is released with unpleasant smell. Both individual spikelets and the entire spike may be affected. Affected ears do not bloom.

In the phase of milky-waxy and full ripeness of the grain, the difference in the color of healthy and affected ears disappears. But in the affected spikelet, instead of a caryopsis, a smut sac (sorus) is formed with a fragile shell of the caryopsis, filled with a black mass of teliospores of the pathogen (photo 4). Such bags are easily crushed and weigh significantly less than healthy seeds. Therefore, in the phase of full ripeness, the affected ears often do not bend towards the soil, but remain straight.

Infection of plants occurs during the germination of spore seeds, before the seedlings emerge to the soil surface. This is facilitated by cold soil (5 ... 10 ° C) with a humidity of 40-60%. Infectious hyphae of germinated teliospores penetrate the wheat seedling. Subsequently, the fungus spreads into the pericarp of the seed, coleoptile, and growth cone. But by the stage of milky ripeness, no significant difference is observed between healthy and affected plants.

The source of head smut infection is contaminated wheat seeds. The seed becomes clogged during harvesting, threshing, transportation and drying of the crop.

Diagnosis of wheat ear infection with smut disease

Regular phytopathological examination of crops makes it possible to establish the dynamics of the infestation of various varieties in order to make further decisions on the use of fungicides and the placement of grain batches on the drain. The degree of damage to the ear by fusarium, septoria and olive mold is determined on a 5-point scale (Table 1).

When inspecting crops, at least 100 plants are selected evenly in different places diagonally across the field. The spread (P,%) and development (R,%) of the disease are determined by the formulas:

P = (n/N) × 100,

R = (Σn × b / N × 4) × 100,

where: n - number of diseased spikelets (pcs.); N - total number of counting ears (pcs.); Σn × b - the sum of the products of the number of ears by the corresponding damage score; 4 - the highest point on a 5-point scale.

It is also important to take into account the presence of mycotoxins, fusarium and soot grain in a batch of wheat grain, depending on its purpose (Table 2).

Protection and measures to combat wheat ear diseases

To protect the wheat ear from the described diseases, a set of agrotechnical and special measures are used aimed at preventing plant infection and seed contamination during the growing season, collection and storage. In particular, they include: growing resistant varieties; properly organized seed production; application of a set of agricultural practices aimed at increasing plant resistance; mandatory disinfection of seed, agricultural machinery and equipment; selection of disinfectants based on testing of seed crops and phytopathological examination of seeds; fungicidal protection of plants during their growing season. The use of recommended fungicides (“List...”, 2014) is carried out on the basis of forecast data for the development of diseases, taking into account the economic threshold of their harmfulness (ETH) (Table 3).

Measures to limit the development of wheat ear diseases

Compliance with scientifically based crop rotation and agricultural technology of a crop and variety is an important phytosanitary factor that prevents or limits the development of diseases.

Compliance with crop rotation. It is recommended to sow wheat (especially seed crops) after fallow, peas, and early ripening soybean varieties. The development of diseases is facilitated by the placement of wheat after cereal grain predecessors and corn. Plant remains of these crops are a good substrate for the accumulation and preservation of infection. Wheat crops after corn are two to three times more affected by fusarium than after peas and soybeans.

Growing resistant varieties. Growing highly productive genetically close varieties of cereal crops on large areas enhances the adaptability and mass distribution of pathogens in agrocenoses. It is believed that bread wheat varieties exhibit higher resistance to fusarium than durum wheat. Also less affected are varieties with a thickened straw, dense cuticle and in which the spikelet scales fit tightly to the grain. Varieties with an extended growing season or flowering phase are more susceptible to disease. As is known, an ear can be infected with ascospores transferred from plant debris in the soil. That's why low-growing varieties are more susceptible to infection than tall people. The best option is to grow not one, but two or three resistant varieties at the same time. Even under favorable conditions for the development of fusarium resistant varieties are able to show tolerance to the disease (not reduce yield).

Phytopathological examination and seed treatment. Direct crop yield losses caused by seed diseases can exceed 20%. Therefore, seed treatment is mandatory event technologies for growing agricultural crops, which makes it possible to protect young seedlings from seed, soil, and in some cases from airborne infections.

Before sowing, seeds are carefully sorted to remove plump and light grains, which are often a source of fusarium pathogens. A phytopathological examination of seed material is also mandatory to establish the species composition of pathogens, the nature of the infection (internal, external or mixed) and the degree of seed damage.

The method of germinating seeds in rolls of filter paper makes it possible to determine its sowing qualities depending on the degree of disease development. Disinfected seeds (100 pcs.) are laid out at intervals of 1 cm on filter paper measuring 115 × 10 cm, moistened to full moisture capacity with sterile water, and secured with a narrow strip of moistened paper. After this, the paper is wound into a roll and placed in glass vessel and place in a thermostat at a temperature of 23 ... 25 ° C. The rolls in the thermostat are periodically moistened.

After 7-10 days, they are unwrapped, the laboratory germination of seeds and the degree of disease development on the seedlings are determined on a 5-point scale: 0 - seedlings without signs of disease and mycelium of pathogens; 1 - normal seedlings, fungal mycelium is formed on seeds and seedlings; 2 - slight darkening of the tissues of the seedlings in the form of streaks or small spots 3 - deformation of the seedlings with solid spots on them and rotting of the tissues; 4 - rotting and death of the seed during germination. The degree of seed damage and disease development is determined using the above formulas.

The effectiveness of seed dressing depends on the correct choice of drug, based on the results of phytopathological examination of seeds (Table 4). It is not recommended to sow seeds with a proportion of fusarium grain above 20%. The presence of smut infection is determined by centrifugation followed by microscopic analysis of the sediment.

Soil treatment against diseases and pests of wheat. The development of diseases is facilitated by the use of no-till systems, surface tillage and shallow incorporation of plant residues. It is also advisable to avoid stacking straw near wheat crops.

Compliance optimal timing sowing, seeding rates and seed placement depths. Sowing wheat at the beginning of the optimal time allows you to accelerate the ripening of plants and avoid severe damage to crops. To avoid smut of durum winter and spring wheat, seeds should not be allowed to fall into cold soil.

Deep planting of seeds delays the emergence of seedlings, which manifests itself in weakening of plants, increased development of root rot and smut. Excessive seeding rates lead to thickening and lodging of crops, and this, in turn, contributes to the development of fusarium.

Providing balanced mineral nutrition carried out on an annual basis agrochemical examination fields taking into account the needs of plants for the planned harvest. The application of high doses of nitrogen fertilizers that are not balanced in other elements often leads to soil toxicosis and the accumulation of pathogenic fungi in it. The latter can enhance the development of root rot and fusarium head blight.

The use of nitrogen fertilizers in high doses increases the development of fusarium head blight by three to seven times. A lack of nitrogen can lead to lodging of wheat; in the presence of rain and high temperatures, it will contribute to the development of diseases. In general, the application of increased doses of fertilizers can prolong the synthesis processes in grain until the phase of full ripeness. This leads to a sharp increase in the nutritional resources of pathogenic fungi, lengthening their development stages on the host plant and the duration of the period of mycotoxin production.

Application of fungicides against wheat ear diseases. Seed dressing (tebuconazole, carboxin, etc.) is used directly against smut. Regarding the control of other described ear diseases, they focus mainly on the most dangerous of them - fusarium. Protection against fusarium head blight, as a rule, makes it possible to limit the development of both septoria and olive mold. Apply one of the recommended fungicides (Table 5) at the beginning of flowering (appearance of the first visible anthers), and, if necessary, again at the stage of milky ripeness of the grain. The choice of timing for treating crops is determined by the fact that the highest development of the disease occurs when plants are infected in the flowering phase, less so when the plants are at milky-wax ripeness. Fungicides of triazole groups are quite effective in protecting wheat from phytopathogens of the genus Fusarium.

Harvesting. At the first signs of fusarium or olive mold, a pre-harvest inspection of crops is carried out in order to determine the degree of infestation of various varieties and the subsequent placement of grain batches on the drain. Affected crops are collected in short time and stored in separate batches. On wet grain, fungi of the genus Fusarium can develop during storage even at a temperature of 3 ... 8 ° C. Therefore, to prevent the accumulation of mycotoxins, it is urgently dried to a humidity of 14%.

A. Dermenko, Ph.D. Agricultural Sciences, Department of Phytopathology, NUBL of Ukraine

Specialists from the Crop Science division of Bayer, together with the laboratory of mycology and phytopathology of the All-Russian Research Institute of Plant Protection, have prepared unique information about a dangerous disease - fusarium head blight; its biology; symptoms; factors that increase the risk of its occurrence; diagnostic methods.

Fusarium is a dangerous and very common disease of plants at any age, caused by fungi of the genus Fusarium

The pathogen, at various periods of plant development, can infect roots, leaves and ears.

Some types of fungi form mycotoxins (from the Greek mukos - mushroom + toxikos - poison) - molecules associated with the secondary metabolism of fungi, which exhibit toxic properties and make it unsuitable for use for food and feed purposes.

Toxins cannot be detected without special equipment, and they can be found not only in grain, but also in its processed products - flour and bread.

SYMPTOMS

Infection of plants with fusarium leads to both a decrease in yield and a catastrophic deterioration in its quality.

SYMPTOMS OF FUSARIA SPEAK BROSIS:

a) pink-orange coating of mycelium and sporulation of the fungus on the glumes of the ear;

b) pale pink sporulation of the fungus on the glumes;

c) eye spot on glumes;

With mild damage, the mycelium is located in the grain shells, while visually the grain is practically no different from healthy ones. But with more pronounced damage, the pathogen penetrates deeper, reaching the aleurone layer and the grain germ. Diseased grains are usually lightweight. Their surface is deformed (“wrinkled”), with a depressed deep groove and pointed barrels, and may have a pinkish tint.

SYMPTOMS OF FUSARIUM GRAIN:

• The affected grains are puny, wrinkled with a depressed deep groove and pointed barrels;
• The surface of the grain is discolored or pinkish, without shine;
• The endosperm is loose and crumbly; low glassiness of the grain or its complete loss;
• In the groove and especially in the embryonic part of the grain there is a cobweb-like coating of fungal mycelium, white or pink, and accumulations of conidia, in the form of pads;
• The grain germ is nonviable, dark in color on the cut.

However, apparently healthy grain can also be affected by fungi and contain mycotoxins!

This disease can cause damage to a batch of healthy and apparently healthy seeds. The presence of a milligram of mycotoxins in a kilogram of grain destroys all its beneficial properties.

CAUSES

Infection of leaves and ears with fusarium occurs by ascospores formed in fruiting bodies on post-harvest residues, or by conidia that appear on stubble residues or on the lower infected leaves. Infection of the ear mainly occurs during wheat flowering in conditions of sufficient humidity and at temperatures above +20°C. This subsequently leads to infection of developing grains.

Factors influencing Fusarium infection

Plants of cereal crops are susceptible to fusarium in the flowering phase at high humidity and temperatures of about +20-25°C (especially F. graminearum). But for species such as Fusarium sporotrichioide and F. poae, increased humidity and air temperature are not mandatory conditions for infection. Weather conditions are an important, but far from the only factor influencing the development of the disease.

CONSEQUENCES

Mycotoxins (from the Greek mukos - mushroom + toxikos - poison) are specific toxic substances produced by fungi. Poisonous macromycetes, such as toadstool and red fly agaric, are well-known “poisoning villains”. But their microscopic relatives (micromycetes) are no less poisonous and even more dangerous. After all, their toxins cannot be detected without special equipment, and they can be found not only in grain, but also in its processed products - flour and bread.

WHAT ARE MYCOTOXINS?

• Mycotoxins are molecules associated with the secondary metabolism of fungi that exhibit toxic properties to humans and animals.
• All major fungal species that cause Fusarium blight can produce mycotoxins.
• Mycotoxins produced by various types of fungi. Fusarium have various toxicological properties.
• Mycotoxins have different effects on different species, such as pigs, poultry, humans, etc.
• The most common mycotoxins in cereals are deoxynivalenol (DON) and T-2 toxin

Distribution of deoxynivaleonol in fusarium wheat milling products

Impact of fusariotoxins contained in feed on the health of animals and poultry

LD50 indicator for mycotoxins entering through the gastrointestinal tract

LD50 is the average dose of a substance that causes the death of half of the members of the test group. LW - live weight
Relative toxicity is the degree of toxicity of a substance in comparison with another substance (in this case, in comparison with T-2 toxin). more toxic substance< 1,0 < менее токсичное вещество

The ability of fungi of the genus Fusarium to cause typical symptoms and produce species-specific mycotoxin

T-2 and HT-2 toxins are among the most dangerous mycotoxins produced by fungi of the genus Fusarium. At the same time, their producers - F. langsethiae and F. sporotrichioides - can develop on the ear without visible signs.

Occurrence of species of the genus Fusarium in grain samples from various regions of Russia

Infection of winter wheat grain with fungi of the genus Fusarium depending on its predecessors

The least favorable predecessor in terms of the subsequent risk of developing fusarium is corn. The presence of such a precursor makes it necessary to develop a strategy for protecting winter wheat from fusarium head blight.

HOW TO DETERMINE FUSARIOSIS?

1. Visual assessment

In areas where the species F.graminearum, F.culmorum, and F.avenaceum are distributed, visible symptoms of fusarium blight on ears can be detected in the field. Infection with fusarium does not always manifest itself visually, but this disease can cause the “disqualification” of a batch of full-bodied and apparently healthy seeds. The presence of literally a milligram of mycotoxins in a kilogram of grain – and that’s it! At best, such grain will be used as fodder. Neither protein content, nor IDC indicators, nor nature matter if the grain contains a microscopic amount of a deadly poison of fungal origin.

ADVANTAGES:
Fast and inexpensive way
FLAWS:
The method is not sufficiently accurate and reliable

2. Mycological analysis

In the laboratory, infected plant parts can be placed on a growing medium that encourages fungal growth.

After a few days of incubation, fungi of the genus Fusarium can be identified under a microscope based on their characteristic taxonomic features.

ADVANTAGES:
Determination accuracy
FLAWS:
Long analysis time
Need for laboratory equipment

3. Principle of polymerase chain reaction diagnostics

PCR is based on enzymatic amplification of a DNA fragment using an enzyme (Taq polymerase).
The chain reaction is a process that occurs in three stages (denaturation, annealing and expansion), repeated in several cycles.
At each stage of the process, the number of copies doubles from two to four, then to eight, and so on. After 20 cycles there are approximately 1 million copies, which is enough material to determine the desired DNA using the traditional method

ADVANTAGES:
PCR is a relatively fast and reliable method for identifying fungi.
Allows you to detect the presence of a certain type or several types of fungi in plant tissue. Detection of the number of fungi is possible using quantitative PCR (real-time PCR).
The amount of fungal DNA detected is related to the presence of mycotoxins they produce.
FLAWS:

4. Planar waveguide technology

A reliable and fast method that uses innovative planar waveguide technology to detect four to five toxins in one measurement.

ADVANTAGES:
Simultaneous determination of several mycotoxins.
Ease of sample preparation
Quick result (25 min)
No special laboratory training required
FLAWS:
Need for specialized equipment

Fusarium of wheat (signs and treatment)

Fusarium blight of wheat is an infectious disease. The causative agent of fusarium is a fungus of the genus Fusarium. This fungus attacks wheat during the flowering period, when the plant is most vulnerable. Wheat flowering lasts only 1-2 days. In rainy weather, the flowering period increases, which means the risk of infection increases. This time is enough to destroy the entire crop.

Signs of fusarium

Fusarium is dry rot of a plant. The main symptoms of fusarium blight in wheat are as follows:

1. The spikelet scales acquire a dark color and become more oily with signs of sporulation. Depending on the region and climatic conditions, sporulation foci have different shades of pink and red.

2. The top or ear is completely covered with a coating of harmful spores.

3. Leaf sheaths and stem nodes contain spore-bearing pads.

4. The grain is covered with white mycelium (mycelium).

Infection of wheat with fusarium occurs during flowering, but signs of fusarium are detected only at the time of grain ripening. The mycelium can damage the grain lightly, penetrating only into the seed coat, or quite seriously, damaging the deep layer. In this case, the process of protein decomposition occurs in the grain.

Wheat grains affected by fusarium have distinctive features:

1. The grains become colorless, sometimes with a pink tint and a dull surface;

2. The surface is wrinkled, with a noticeable coating of mycelium in the groove;

3. The seed becomes fragile, the glassiness decreases, the embryo dies, which can be seen as a dark dot on the cut.

Causes of infection

1. Sowing wheat without taking into account predecessors;

2. Poor field cleaning;

3. Poor tillage;

4. Infected seed, failure to treat seeds before sowing.

I would like to immediately note that infected seeds cannot germinate; therefore, if the seeds germinate, and then foci of fusarium appear on the field, this indicates that at the time of sowing the sprouted seeds were completely healthy and became infected later.

Seeds infected with fusarium and not sprouting are dangerous because they can contribute to the spread of spores. Therefore the only thing the right decision, and everyone should remember this, it is mandatory to treat the seed with multicomponent fungicides before sowing. This will prevent the development of spores (if any) in the seeds, and will protect the seeds when sowing from fusarium in the ground.

Most common reasons Fusarium infections of wheat are:

1. Selecting a wheat variety without taking into account the predecessor;

2. Poor field harvesting and shallow tillage;

The above reasons contribute to the development of fusarium in the soil itself.

When sowing wheat, it is necessary to look at which predecessor is used to sow. For example, if you previously grew corn, we under no circumstances recommend sowing wheat next: Bagrat, Vassa, Grom, Yubileinaya 100, Dmitry. The following wheat varieties are allowed for sowing corn: Lebed, Bezostaya 100, Esaul, Sila, Tanya, Yuka, Urup. They are more resistant to fusarium, however, among them there are no varieties that are absolutely not susceptible to the fungus. Therefore, wheat still requires preventive treatment.

Most often, poor field harvesting and shallow tillage contribute to the preservation and spread of mycelial spores. The All-Russian Institute for Plant Protection published data: when plowing the soil with rotation of the layer, the soil infection with fusarium was 15%, while during surface tillage the infection with fusarium was almost 49%.

Due to the fact that fusarium mycelium spores comfortably survive the winter on plant debris, after harvesting the field must be cleaned and the plant debris plowed. This way, the fusarium pathogens will die in 3-5 weeks, which means the risk of crop contamination will be reduced.

Methods to combat fusarium

To avoid purchasing low-quality seeds, when choosing a supplier, you can request from him not only wheat certificates, but also seeds for testing. You can then submit them to a laboratory for testing for the presence of pathogens. seed material. Of course, there will be a fee for the analysis, but you will definitely be sure of the quality of the seed material. After conducting tests and making sure that the seed is clean, do not forget that the main source of infection is the soil itself, and not the seeds, and buying clean, healthy wheat will not protect the crops from infection during flowering. Fusarium, like a fungal disease, begins to spread in the soil, and then, with the help of the wind, the spores begin to spread throughout the field.

According to GOST, wheat seeds are sold in pure form without the use of chemicals. processing. Therefore, when purchasing new seeds, it is necessary to treat them with fungicides before sowing. You can do this either on your own, or, if you take the seeds directly from the manufacturer, order additional dressing. In this way, you will prevent the proliferation of spores if, nevertheless, samples with signs of fusarium are found among the seeds, and also protect the wheat from infection when the soil is affected.

We must not forget that seed treatment is only the first stage of protection. During the growing season, it is necessary to spray wheat repeatedly (at least 2-3 times) before the ear blooms, because Fusarium spores are carried across the field by the wind. And during flowering, when the ear is most susceptible, it is infected.

The most important thing in treating with fungicides is to choose the most suitable product. The use of fungicides on winter wheat makes it possible to further preserve the green surface of the leaves, and most importantly, helps to maintain the flag leaf of wheat in a functioning state during the grain filling period.

The effectiveness of fungicides can be increased using biological products. However, they should not be completely replaced, because... The potency of biological products is still lower than that of fungicides, which means that the risk of field contamination and crop loss increases, and the environmental purity of the product becomes questionable.

If, nevertheless, fusarium was not prevented and for some reason foci of fusarium appeared in the wheat fields, unfortunately, any fight will be unsuccessful. In this case, harvesting should be done separately, and based on a random (average) sample, the percentage of fusarium in each batch should be determined. In accordance with GOST and Technical regulations The Customs Union TR CU 015 “On the safety of grain” accepts wheat grain with a fusarium content of 1% for food purposes. For cereals and flour production, it is allowed to use strong wheat grain with a fusarium grain content of up to 0.6%; other wheat may contain contaminated grains of up to 0.3%. To comply with sanitary standards, before processing grain in which the content of fusarium grains is up to 1%, it is necessary to reduce the concentration of fusarium grains in the total mass to the permitted level by adding healthy grain not infected with fusarium.

Grain infected with fusarium over 1%, but not more than 10%, is used for feed purposes for the production of compound feed and feed mixtures. When fusarium blight exceeds 10%, the wheat is sent for destruction.

Conclusion

Fusarium is a plant disease, the source of which is most often the soil. It is easier to prevent than to neutralize it. This will require preventive actions before sowing in the form of seed treatment to prevent the development and spread of spores. It is also necessary to prepare and cultivate the sown areas, removing plant residues from the previous harvest. After sowing, wheat should be treated with fungicides at least 2-3 times until the wheat blooms. And, of course, the fact of the correct choice of the wheat variety that is most suitable for its predecessor is not unimportant. Having fulfilled all these conditions, you can fully count on good harvest, and therefore a good profit.

Fusarium is a global problem. Diseases that occur when various cereal crops are infected by certain species of pathogenic fungi of the genus Fusarium are among the most serious and potentially destructive diseases throughout the world and especially in the regions of the USA, Canada, Argentina, Australia and Europe, including. Ukraine, engaged in the cultivation of wheat. Since the early 90s, there has been a sharp increase in the incidence of diseases caused by a pathogenic fungus of the genus Fusarium. The risk of infection has increased due to changes in crop growing technology: for example, the increasing use of minimum tillage technology; increasing the frequency of sowing grain crops in crop rotation, as well as as a result of increasing the area under corn. Infectious lesions caused by a pathogenic fungus of the genus Fusarium can occur at the base of the stem, on the leaves and on the ears. The greatest damage is caused when the pathogenic fungi Fusarium graminearum and F. сulmorum infect the ear. Because these pathogenic fungi produce mycotoxins, they can directly limit the use of contaminated grains in food and feed production. Mycotoxins are dangerous for people and animals. Fusarium ear blight leads to a decrease in the weight of a thousand grains and the number of grains in the ear, and also reduces the viability of seeds. Crop losses can reach more than 50%. This disease also reduces the baking quality of flour and can negatively affect the brewing process if infected barley is used in it. However, an even more important factor is the ability of the pathogenic fungus Fusarium to produce mycotoxins, that is, products of the fungal metabolic processes that are toxic to humans and animals and can cause serious damage to the body, even in small concentrations. The most dangerous fusariotoxins that are produced in cultivated cereals are nivalenol, deoxyny-valenol - mainly in wheat, triticale and barley. Wheat, barley and rye are especially vulnerable. Typical sign: discoloration of the ear Infection or re-infestation caused by F. graminea rum and F. culmorum leads to the discoloration of an ear or a whole group of ears. A brownish-purple color is also often observed on the central axis of the ear. If weather conditions are favorable for the development of the fungus, then spore bodies are formed at the base of the ear and at the edges of the spike scales, the color of which ranges from orange-red to pink. Signs of the disease may differ depending on which cereal crop is affected by this disease - wheat, triticale, oats, rye, spring or winter barley. Infection with conidia and ascospores. Pathogens, mainly in the form of conidia and ascospores, overwinter in fields on dead plant debris such as straw and stubble. Conidiospores can infect the ear after being spread from letter to letter up the stem by raindrops, but wind-borne ascospores also play an important role in direct infection of the ear. Ascospores develop in fruiting bodies called perithecia. These fruiting bodies form on contaminated organic debris located on the soil surface. Over time, the perithecia mature and disperse ascospores. If cold and wet weather persists for a long time after the spores are released, an asymptomatic increase in the number of spores may occur. Since ascospores can only spread over very short distances, the source of infection in a particular field is usually a potentially contaminated object present in that field. The danger of infection depends on whether the crops are located near the epicenter of infection at the time of spore release. The most susceptible to them is the flowering phase, when the pathogen's spores have just matured and they easily penetrate the plant tissue. The main routes of infection are the anthers, ovaries, and the inner surface of the spike scales. After successful infection, the development of the fungal mycelium inside the plant tissue begins towards the stem. When the infection is severe, the pathogen produces a large number of mycelium, which is deposited in the vascular conduction system of the stem. As a result, partial or complete discoloration of the ear or white-headedness occurs. The extent of infection depends on weather conditions and pathogenic potential. The most important factors influencing the incidence of Fusarium pathogen infection are the precursor, tillage quality, cultivar selection, weather conditions and fungicide use. Two of these factors - predecessor and soil treatment - have a significant influence on the magnitude of pathogen accumulation potential. The combination of the initial pathogenic potential and weather conditions, in turn, determines the accumulation of the pathogen, which can subsequently lead to the occurrence of fusarium head blight. The danger of Fusarium infestation also depends on the agricultural perception (stage of development/varietal resistance) and timing of fungicide application. The occurrence of infection is especially favored by variable and rainy weather during the heading period. In order for destructive pathogens such as Fusarium fungi to infect a plant, it is enough for them to have a wet period of 24 to 40 hours at temperatures above 20 ° C. Rainfall levels of only 3-5 mm at minimum temperature 16-18 ° C during the flowering period of wheat can create a very high risk of infection outbreak. Different kinds Fusarium fungus differ from each other mainly in the requirements for the temperature at which infection occurs (F. сulmorum: 16-18 ° C; F. graminearum: 20-22 ° C). Warm and humid weather between the flowering and ripening of grain crops, combined with their late harvest, create the preconditions for the spread of pathogens and contamination of grain with toxins. Main source of infection: corn stubble in short rotation crop rotation. Stubble, as well as other plant debris that remains on the soil surface, especially corn stalks, which are difficult to decompose, are a source of infection throughout the growing season; thus, the risk of infection of further crops increases. So, tillage with minimal mechanical action greatly contributes to the occurrence of infection: depending on the technology and treatment method used, most of the plant residues remain on the soil surface and in its surface layer. According to a study in France, when direct-seeded wheat was harvested after corn, its deoxynivalenol content was four times higher than that of wheat sown after tillage. With minimal tillage, the content of toxins in the soil was twice as high as with plowing. It is absolutely clear that incorporating stubble into the soil by plowing significantly reduces the risk of infection. However, the stubble that was previously in the soil and during the plowing process, when preparing the soil for the subsequent crop, again fell on the soil surface, still remains a source of infection if it is not completely rotten. The greatest risk of infection is if wheat is direct seeded after corn. The second very risky method, although with a much lower degree of risk, was hanging wheat by direct sowing into the stubble after the predecessors of cereal grains. Various strategies must be used to reduce infestation Farmers need to apply certain agronomic measures to avoid infection of crops with the Fusarium fungus, since the crop should not contain toxins in concentrations exceeding permissible level infection. Depending on the location and other factors, the following actions should be taken to reduce the incidence of infection: Careful selection of crops in the crop rotation: reduce the amount of corn or grain crops in a long-rotation crop rotation.

Variety selection: growing varieties that are less susceptible to the Fusarium fungus; Stubble management: Tilling the soil reduces the risk of infection; also, crushing and uniform distribution of plant residues of agricultural crops accelerates the process of their decomposition in the soil with the help of microorganisms (which proceeds even faster when ammonia urea is added to the soil);

Fertilizing agricultural crops: Poor crop development and lodging (both of which can increase plant susceptibility to infection) should be avoided by applying fertilizers according to crop-specific requirements. Harvesting the crop as soon as the grain has reached the required stage of ripening (sufficiently low moisture content);

Application of plant protection products: use of fungicides.

Treating seeds with disinfectants, spraying leaves and ears with appropriate preparations (which include active ingredients such as tebuconazole, prothioconazole: Lamardor, Raxil Ultra, Falcon, Folicur), which reduce infectious loads. Effective fungicides are already available, but weather conditions remain the main factor that determines the occurrence of infestation. If conditions are conducive to infection, farms have little choice but to use fungicides to control Fusarium fungus to reduce infestation and, most importantly, reduce mycotoxin production. When lesions caused by this pathogen are already present at the time of treatment of the leaves, it makes sense to use a drug containing components that are effective against the Fusarium fungus - Falcon, Folicur. Such actions can lead to a significant reduction in infection by this pathogen and a reduction in contamination by mycotoxins. Based on the results of tests in which ears of cereal crops were treated with azole fungicides (containing components such as tebuconazole or prothioconazole as active ingredients), it was clearly proven that when crops were treated at the appropriate time, the degree of Fusarium damage to the ear, and accordingly, the level of toxin contamination , can be significantly reduced. In field trials over several years in France, Germany and the UK, Falcon significantly reduced infections by the pathogenic fungus Fusarium in more than half the wheat varieties studied, and also reduced deoxynivalenol content in grain by an average of 50%. The timing for treatment is highly dependent on the species of pathogenic Fusarium fungus and the weather conditions required for infection. All this means that time for optimal treatment of crops with fungicides is limited. Best time for the use of drugs during flowering - after one or two days from the moment of infection with the pathogen. First of all, after rain, after the beginning of the appearance of ears (when approximately 30-40% of ears have appeared). Spraying may be less effective if it is carried out only a few days earlier or later than required. Tests carried out over several years have shown that optimal time for use of drugs, on average, within three days before flowering and three days after flowering. However, the occurrence of infection caused by the pathogenic fungus Fusarium can be successfully reduced by using the drug Falcon.