Occurrence and Control of Wheat Scab

Wheat scab is one of the important diseases that affect wheat yield. In recent years, all wheat regions in the country have occurred to varying degrees, and the average year of production can reduce production by 5%-15%. The early death of the damaged wheat ears, grain shrinkage, small grain size, whitish grain color, not only greatly reduced wheat yield, but also deteriorated quality, low powder extraction rate. When the diseased grains are seeded, the germination rate is reduced. Although germination is possible, the seedlings are yellow and thin, and they easily die.
1. Performance Symptoms Head blight may occur from seedlings to heading, causing seedling emergence, ear rot, base rot and culm rot, of which ear rot occurs most commonly and severely. Seedling Blight: Caused by seeds or soil residues. The diseased seedlings first became brown and decayed, and then the root cap rotted. The diseased seedlings were yellow and lean until they died. When the humidity in the field is high, the stem of the withered seedlings can produce pink mold. Spike rot: Occurs after flowering in wheat. Water-stained brown spots appeared on the spikelets and glumes at the beginning, spreading gradually to full spikelets, and the spikelets then turned yellow. At the early stage of disease, at the base of spikelets and at the base of spikelets, there is a layer of pink glial layer, and at the later stage, blue-black particles are produced at the pink mold layer, and the grains within the diseased spikelets shrink and dry. There is white to pink mold. A common wheat ear usually has a small number of spikelets and then quickly spreads to the cobs to make the disease brown. Base rot: It is the base tissue of the plant stem that becomes brown and decays after the victim suffers and the whole plant withers. The root rot usually begins to infect from the seedling stage, but also occurs during the mature period of the plant. When the diseased seedlings are pulled up, they often break off from the rot of the stem base, and brown decayed decayed tissue appears on the fracture surface. Silk soil and other things. Stem rot: generally in the first and second section of the ear disease, leaf sheath first appeared immersed chlorotic spots, after the expansion of light brown irregular lesions, yellow disease above the Department, or even normal heading.
2. Incidence conditions The occurrence and epidemic of wheat scab are affected by factors such as climatic conditions, number of bacteria, species and cultivation conditions. Fusarium head blight to a wide range of temperature adaptation. The optimum temperature for mycelium development is 22-28°C, the lowest is 3°C, and the highest is 35°C. The relative humidity of the air is relatively high, and the germination rate of the ascospores is highest when the relative humidity of the air is 80-100%, and the germination rate is lower than 72%. Therefore, when the spring is warmer and early, the humidity in the field is high, especially in the years when the wheat blooms in the rain, it is extremely beneficial to the occurrence of head blight. When extensive cultivation and management, large number of sick bodies remain in the fields, or over-application of nitrogenous fertilizer causes excessive density of wheat, the young crops that are plagued with vulgarity tend to be lodging, and as long as the conditions are appropriate, it is easy to develop diseases.
3. Control measures
(1) Selection of disease-resistant varieties. At present, immunization varieties are still found in wheat production, but there are differences in resistance among different varieties. The degree of onset of the same species in different regions or different years is also very different. Short heading, neat flowering, short flowering period, small angle of opening of glume, shorter filaments, sparsely populated varieties, and lighter disease incidence, even if infected, are limited to infected spikelets and their adjacent spikelets; Thicker, longer flowering varieties tend to be more severe.
(2) Chemical control. Since wheat scab is mainly based on ear rot attack, the control of pesticides should be in the stage of heading to filling of wheat. The appropriate period and number of spraying should be based on the weather forecast before and after the heading date of local wheat and the number of occurrence of wintering germs. (It refers to the rate of clumps of plant residues) and its maturity, and makes correct predictions, but it should focus on the first application of wheat. In general, the first application should be from heading to full bloom. However, in the warm and rainy season should be earlier, the first spraying should be carried out as early as the booting stage. In order to suppress the infestation of ascospores in time and to prevent rainwater from eroding the liquid, it is necessary to fight for the first time before the rain to clear the weather. Otherwise, we must also pay close attention to remedy in the rain stop gap. Generally should master the principle of "Ninghai not too late". Practice has proved that the use of drugs with high efficacy and residual effects, such as thiophanate-methyl, carbendazim and other bactericidal drugs, has a good control effect. Generally, carbendazim or thiophanate-methyl is used as an active ingredient in an amount of 40-50 grams per acre in wheat. Spreading evenly in the ear of wheat at full heading stage can achieve more than 90% control effect.
(3) Agricultural control. Appropriate sowing, reasonable fertilization, cultivating strong seedlings before winter, improve plant resistance to disease. Strengthen field management, rational irrigation, ensure that wheat heading and flowering are tidy, and shorten the time of pathogen infection. Doing a good job of monitoring and reporting, and doing a good job of field drainage in the rainy season can reduce the occurrence of diseases. In addition, cultivating stubble and cleaning the pasture can reduce the source of germs.

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