Hard smut of wheat is a very dangerous disease, significantly reducing the yield of this crop. Such an infection is widespread, unfortunately, in almost all agricultural regions of Russia. In other words, the smut is called smelly or wet.
Key features
The causative agent of wheat smut 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 features of such smut are:
- slight flattening of ears;
- bluish tint in the green part of the plant.
The scales of infected ears are slightly apart. When crushing grains of diseased plants, it is not “milk” that is secreted, but a grayish fetid liquid.
As the wheat ripens, the color difference between healthy and infected ears gradually disappears. However, diseased plants remain upright. This is due to the fact that instead of grain in infected ripened ears, smut smacks are found that are light in weight. The color of these formations are dark and they consist of a huge number of dusty spores.
How infection can occur
One of the distinguishing features of sorts 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 healthy seeds, they linger in their beards. Thus, the infection of the seed occurs.
When infected seeds are planted, smut spores enter the soil and germinate, forming basidia. On each such tube, 4-12 basidiospores subsequently appear. After copulation of the latter, infectious hyphae are formed that can penetrate the tissues of germinating wheat.
Subsequently, the mycelium gradually increases upward, infecting the stem, leaves and ears. At the very beginning of its growth, mycelium does not spread very actively. However, in the stage of milk ripeness of 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. Unlike, for example, dusty, spores of solid smut are kept in capsules quite tightly. Dark formations in ears are scattered, usually only when 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 in this way can occur mainly only when new wheat is sown on the field no later than 3 weeks after harvesting the old. But sometimes, under favorable conditions, smut spores can persist in the soil for up to 2 years.
The main causes of infection
Damage to this disease in wheat can be simply enormous. The yield on the field infected with solid smut is falling not only due to grain loss, but also due to the death of plants. Also, this disease reduces the immunity of plants. Because of this, wheat tolerates the winter worse and becomes more susceptible to other infections.
The risk of infection of cereals with solid smut significantly increases with:
- Seeding too deep when planting;
- during prolonged autumn drought;
- if the timing of sowing is not respected.
Scientists have revealed that smut spores germinate best at a temperature of 2-5 ° C. Therefore, infection of early spring wheat planted in spring or winter wheat is too late in autumn is faster.
With a deep planting, the seeds of this grain crop sprout for a long time. As a result, the risk of penetration of mycelium into the ground sharply increases.
Wheat smut control measures
It is believed that spring cereals are most susceptible to infection with this fungus. But winter wheat is infected with spores of this fungus, unfortunately, also quite often. In any case, measures aimed at preventing the spread of fungus in crops should be observed both during spring and autumn planting.
In order to prevent crop losses associated with smut infection, wheat varieties resistant to this disease should first be selected for cultivation. Also an effective measure to combat this fungus is preplant seed treatment.
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. Infection with cereal mycelium occurs only in the first 8 days after germination. Subsequently, the wheat becomes firm against smut.
Of course, grain should be selected as planting material only from fields that are favorable in terms of this disease. Typically, on farms, crops infected with smut by more than 0.3% are transferred to commodity ones.
Seed dressing and equipment disinfection
For the processing of planting material in order to prevent infection by smut, various fungicides are usually used. Moreover, TMTD and pentatiurams are most often used. It is believed that dressing requires seeds collected from fields where crops are affected by at least 0.0001-0.0004%. At the same time, planting material must be processed no later than 15 days before sowing. Most often, fungicides are used to etch grain from this fungus, for example, Raksil, Vintsit, Vitovaks, etc.
During harvesting and threshing, the bunt spores can remain, including on the working tools of agricultural machines and containers. All of these items, of course, should also be disinfected to prevent infection of the seed with the fungus. An inventory is worked out to prevent smut wheat infection, usually using a 1% formalin solution.
Other types of disease
Solid smut at the moment in Russia is not distributed as much 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 variety of fungus that can reduce wheat productivity. In addition to hard, cereals in Russia can be infected with the following smut types:
Signs of different types of smut
A characteristic feature of Indian smut of wheat is that its manifestations, unlike hard, can be clearly visible already during flowering.
When plants are infected with a dusty variety of fungus, only the lower parts are affected mainly. Dwarf smut, like solid smut, is manifested by the replacement of grain with capsules with a black mass of spores. But when infected with this variety of fungus, the ear is completely deformed. With the stem smut of wheat, the leaves of the plant are twisted in a loop.