Causes of wheat rust and methods of combating it

According to experts, rust is considered one of the main and most dangerous diseases of wheat. All above-ground parts of the plant are affected: leaves, stems, ears. There are many causes of infection, so to preserve crops, experts are constantly developing new effective methods to combat the harmful pathogen.

Features of the disease

Wheat rust is caused by the basidiomycete fungus Puccinia recondita.. The disease manifests itself in the form of yellow, black and brown small blisters (pustules) on the leaves and stems of the plant, in which fungal spores develop.

Initially, the pustules are covered by the epidermis. As the disease progresses, they burst and release yellow or orange powder—spores—that disperse to and infect nearby plants.

Why is it dangerous for wheat?

Externally, the spores resemble rust. They stop the process of photosynthesis in plant tissues and lead to a decrease in the ability of wheat to produce grain.. By introducing itself into the cells of a plant, the pathogenic fungus does not kill it, but begins to take away the nutrients necessary for development and growth.

Such destructive processes cannot but weaken the culture. Besides:

1. Damaged leaves die prematurely, and stems break and lie down.
2. The root system is poorly formed, and therefore does not provide the plant with enough moisture.
3. Due to the rupture of the epidermis in the affected areas, the water and respiratory balance of the plant is disrupted.
4. The culture loses its resistance to drought and frost.
5. The development of grain in the ear is delayed - its quantity and weight are significantly reduced.

The infected plant becomes weak and punyAccordingly, the yield decreases.

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Kinds

The most common and dangerous types of wheat rust include:

• stem (linear);
• leafy (brown).

Stem can infect up to 300 species of cultivated and wild cereals. The stems and internodes are the first to suffer. Later it affects the sinuses (vaginas) of the crop, and less often - leaves and parts of the ear.

Leaf rust infects winter and spring wheat, as well as other cereals. The leaves and axils of plants are mainly affected. During the growing season of crops, several generations of fungal spores develop, which, scattering, infect an increasing number of plants, and therefore can cause massive damage to crops.

Leaf rust causes the greatest damage to winter wheat. Crops infected in autumn do not survive winter well. With the onset of spring, a noticeable difference is noticeable between sparse, rusty plantings and healthy ones that have safely survived the winter period.

Causes

The main reason for widespread rust damage to wheat is high viability of fungal spores and their rapid and widespread distribution.

Sources of infection and favorable conditions for development

Sources of spread of the disease are plant residues, infected weeds or forage cereal plants. and intermediate ones, in particular basilisk and hazel. Additional foci of infection may be affected rye, barley, bluegrass, meadow fescue and other wild cereals. Spores are also carried by gusts of wind from distant, heavily infected crops.

It is not only stem and leaf spores that survive the winter on infected stubble, but also many other types of rust, which in the spring cause a new wave of the disease.

Important! Many varieties of fungus also develop on the carrion of cereals during the period from harvesting to the germination of winter crops. Therefore, fallen grains pose a great danger to winter crops and act as an intermediate carrier of infection.

Conditions favorable for fungus also contribute to the spread of rust.:

1. The presence of an infectious background (carrion, infected stubble, plant debris, etc.).
2. Early plantings of winter and late spring wheat contribute to the development of stem rust.
3. Application of high doses of nitrogen fertilizers.
4. Cool and wet weather in August and September, mild winter, cool spring and first ten days of summer.
5. Intense precipitation in the first half of the growing season and during the heading period.
6. Presence of dripping moisture (dew or evening rains).
7. Thickening and infestation of crops with cereal weeds.

Wheat rust fungus can infect crops over a wide temperature range — from +2°С to +30°С. The maximum rate of development and spread of the disease is observed at +15…+24°C.

Important! More often, outbreaks of infection occur after prolonged rains at air temperatures of +20...+25°C.

Geography of distribution

The mushroom is widespreadTherefore, the cultivation of wheat is always associated with the danger of massive infection of crops. In the northern regions and Siberia, where summers are not so hot, spores are preserved better, therefore, the danger of the disease increases.

Linear stem rust of cereals is especially common in regions with humid, warm climate. The most susceptible areas are the North Caucasus, the Far East, the Baltic States, Western Ukraine and Belarus.

Leaf, or brown, rust of wheat occurs in all regionswhere there are wheat fields.

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Symptoms of the lesion

Stem rust usually appears on cereals after flowering, less often in autumn or spring on seedlings of winter crops. Externally, the disease is determined by longitudinal stripes or lines that are formed from the fusion of clusters of single-celled orange uredospores on the affected organs of the plant. Therefore, stem rust is also called linear rust. The disease causes increased transpiration (evaporation of moisture) and leads to drying and falling of leaves.

Leaf rust appears as rusty-brown round or oval, dusty, chaotically located pustules measuring 1-1.5 mm. They do not merge into solid spots, as with a stem infection. Later, the pustules become black with a glossy tint. With severe development of the disease, almost the entire leaf blade is affected, a burn occurs and the leaves curl.

The first symptoms of the disease on winter crops can be noticed in the fall, however, they become clearly noticeable in the spring before the heading stage.The peak of rust development occurs during the period of milky-waxy grain ripeness.

Fighting methods

There are three main types of struggle with this disease.

Biological

These methods of protection are absolutely harmless from an environmental point of view (unlike chemical ones). List of actions:

1. Creation of rust-resistant varieties by specialists.
2. Analysis of plant and soil samples from an infected field to identify a specific strain of pathogens and selection of appropriate fungicides.
3. Colonization of the soil with beneficial microflora using microbial preparations “Fitostim”, “Agrovitastim”.
4. Measures to decompose infected plant residues using the bacterial preparation “Stimix”, which suppresses pathogenic microbiota, preserving all the valuable microelements of stubble in the soil.
5. Regular monitoring by analyzing samples of soil microflora for timely prevention of fungal infection.

In the initial stage of disease development, it is necessary to spray the crops biological preparations "Planriz" and "Agate".

Agrotechnical

Basic measures to combat rust:

1. Destruction of sources of infection.
2. Spatial isolation of spring and winter wheat crops. Infected winter crops are the source of the disease, from where it spreads to spring crops.
3. Replacement of varieties with more resistant ones: wheat Timofeeva, Bezostaya 1, Bezostaya 2, Caucasus.
4. Application of additional doses of phosphorus-potassium fertilizers for grain crops, which increase the stability of the crop.
5. Fertilizing, accompanied by loosening of row spacing, is effective for improving the health of plantings.
6. Optimal sowing dates for spring and winter wheat.In the European part of Russia, the best results are obtained when spring sowing is done early (usually in April), when the soil warms up to +5...+6°C. For winter wheat, favorable conditions for sowing occur when the average daily air temperature is +14...+15°C (approximately from September 25 to October 5). In this case, the plants have time to go through the early phases of development in conditions unfavorable for rust.
7. Timely harvesting of grain. At later stages, overripe grain, which may contain infected specimens, spills out of the ears and remains on the soil, and in the spring it becomes a source of infection.

Chemical

When rust symptoms are detected, crops are sprayed from airplanes with fungicides of groups:

• strobilurins: “Uniform”, “Altruist”, “Triaktiv”, “Amistar”.
• triazoles: Tebuconazole, Tetraconazole, Propiconazole.
• benzimidazoles: “Fundazol”, “Benazol”, “Alternative”, “Benomil”.

As a result of exposure to fungicidal drugs, fungal spores are lost ability to germinate.

Preventive measures

In order to prevent the development of infection caused by stem and leaf rust fungi, measures are taken:

1. Regularly inspect the condition of plant leaves, especially during the period of ear formation.
2. The seed material is treated with the fungicides “Baktofit”, “Fitosporin-M”, “Dividend Star” and “Viatsit”. The procedure increases the stability of the crop and reduces the harmfulness of rust and other diseases.
3. Follow the rules of crop rotation. Favorable predecessors are legumes (clover, alfalfa, peas) and row crops (corn, cotton, potatoes, sugar beets, etc.).
4. They use rust-resistant wheat varieties: Brigantina, Obriy, Moskovskaya 35, etc.
5. The stubble is peeled (the top layer of soil is turned over during harvesting) followed by autumn plowing of the soil.

Conclusion

Despite the fact that rust does not destroy the grain itself, the harm it causes is extremely great. Infection of cereals occurs throughout the entire growing season, which significantly affects the yield. Only by studying the causes of infection in a certain area and competently drawing up a set of measures to combat the fungus can you get rid of a dangerous pest of winter and spring wheat.