Common smut of wheat: causes and methods of control

2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16

Common smut of wheat is a very dangerous disease that significantly reduces the yield of this agricultural crop. Unfortunately, such an infection is widespread in almost all agricultural regions of Russia. In another way, hard smut is called smelly or wet.

Key Features

The causative agent of durum bunt of wheat is a fungus from the genus Tilletia. You can clearly notice the symptoms of this disease only at the very beginning of the milky degree of grain. The main signs of such a smut are:

• slight flattening of ears;
• bluish tint in the green part of the plant.

The scales of infected ears are slightly spread apart. When crushing the grains of diseased plants, not "milk" is released, but a grayish, fetid liquid.

As the wheat ripens, the difference in color between he althy and infected ears gradually disappears. However, diseased plants remain upright. This is due to the fact that instead of grain in infected ripe ears, smut sori are found, which have a small weight. These formations are dark in color and consist ofthey are from a huge number of dusty spores.

How infection can occur

One of the hallmarks of sori is fragility. When threshing grain, they are easily destroyed. This, in turn, leads to the fact that spores spill out into the environment. Getting on he althy seeds, they linger in their beards. This is how the seed becomes infected.

When infected seeds are planted, smut spores enter the soil and germinate, forming basidia. Subsequently, 4-12 basidiospores appear on each such tube. After copulation of the latter, infectious hyphae are formed that can penetrate the tissues of germinating wheat.

Subsequently, the mycelium gradually increases upwards, infecting the stem, leaves and ears. At the very beginning of its growth, the mycelium does not spread very actively. However, at the stage of milky ripeness of the grain, its development is strongly activated. Therefore, the signs of the disease during this period become clearly visible.

Sometimes, infection of planted wheat can also occur with spores located directly in the soil. However, plants are rarely infected in this way. In contrast, for example, from dusty, spores of hard smut are held in capsules quite tightly. Dark formations in the ears usually crumble only during threshing.

The spores of this fungus that fell into the ground during wheat harvesting are also, in most cases, quickly neutralized by soil microorganisms. Infection can occur in this way mainlyonly when new wheat is sown in the field no later than 3 weeks after harvesting the old one. But sometimes, under favorable conditions, smut spores can persist in the soil for up to 2 years.

Main causes of infection

The damage this disease can cause to wheat is simply colossal. Yields in a field infested with hard smut fall not only because of the loss of grain, but also because of the death of plants. Also, this disease reduces the immunity of plants. This makes wheat less resistant to winter and more prone to other infections.

The risk of infection with boar smut in cereals increases significantly when:

• too deep seed placement when planting;
• during the long autumn drought;
• in case of non-observance of the terms of sowing.

Scientists have found that smut spores germinate best at a temperature of 2-5 °C. Therefore, early-spring-planted spring or late-autumn-planted winter wheat infect faster.

When planted deep, the seeds of this grain crop germinate for a long time. As a result, the risk of mycelium penetration into them underground increases sharply.

Wheat smut control measures

Spring cereals are believed to be most susceptible to this fungus infection. But winter wheat is infected with spores of this fungus, unfortunately, also quite often. In any case, measures aimed at preventing the spread of the fungus on crops must be observed during both spring and autumn planting.

In order to preventyield losses associated with smut infection, wheat varieties that are resistant to this disease should be selected for cultivation in the first place. Also, an effective measure to combat this fungus is preplant seed dressing.

Of course, in order to prevent infection of plants, it is necessary to strictly observe, among other things, the timing and technology of planting wheat. Grain mycelium infection occurs only in the first 8 days after germination. In the future, wheat becomes immune to hard smut.

Of course, as planting material, grain should be selected only from fields that are safe in terms of this disease. Usually, on farms, crops infected with smut by more than 0.3% are transferred to commercial crops.

Seed dressing and inventory disinfection

For the treatment of planting material in order to prevent infection with smut, various kinds of fungicides are usually used. In this case, TMTD and pentatiuram are most often used. It is believed that dressing requires seeds collected from those fields where crops are affected by at least 0.0001-0.0004%. At the same time, planting material should be processed no later than 15 days before sowing. Most often, fungicides such as Raxil, Vincit, Vitovax, etc. are used to treat grain from this fungus.

During harvesting and threshing, hard smut spores can also remain on the working tools of agricultural machines and containers. All these things, of coursehowever, to prevent infection by the fungus, the seed should also be disinfected. Treat inventory to prevent smut infection in wheat, usually using a 1% formalin solution.

Other diseases

Solid smut is currently not as widespread in Russia as, for example, in the middle of the last century. In the 60s in the USSR, crop losses due to this disease often reached 30%. However, this infection can still cause significant damage to crops. And of course, this is not the only type of fungus that can reduce the yield of wheat. In addition to solid smut, cereals in Russia can be infected with the following types of smut:

• Indian;
• dusty;
• dwarf;
• stem.

Signs of different types of smut

A characteristic feature of Indian wheat smut is that its manifestations, in contrast to durum, can be clearly seen already during flowering.

When plants are infected with a dusty fungus, only the lower parts are affected. Dwarf smut, like hard smut, is manifested by the replacement of grain with capsules with a black mass of spores. But when infected with this type of fungus, the ear is completely deformed. With stem smut of wheat, the leaves of the plant curl in a loop.