In recent years, the occurrence of wheat sheath blight has been increasing year by year. It has become the main disease of spring wheat field in many places, resulting in serious loss of wheat yield. The main reason is that wheat varieties, cultivation systems, fertilizer and water conditions have changed, and management has not been timely. Keeping up, in the presence of a large number of bacterial sources, it presents the characteristics of early onset and rapid emergence, which brings great pressure on prevention and treatment. Therefore, the prevention and control of wheat sheath blight after spring should be highly valued.
First, the characteristics of occurrence
Wheat sheath blight is caused by the fungus Fungi of the genus Aspergillus. The pathogen is sclerotial with the diseased residue or in the soil for summer and winter. Wheat seeding begins to infect, usually after the jointing of wheat, and it continues to infect and re-infect, generally warm and humid in spring is conducive to the onset. The course of wheat sheath blight can be divided into several periods:
One is the beginning of the disease before winter. When the wheat seedlings are in the second leaf stage, they mainly occur on the base sheath. In the rainy year after sowing, the rate of diseased plants in the field before winter is about 5%, and that in early sowing fields can reach 15%~20%.
The second is the wintering period. As the temperature drops below 10 °C, the condition develops slowly or stops.
The third is the horizontal expansion period. In the spring, as the temperature rises, the number of diseased plants in the field increases. At this time, the more rain, the more serious the disease.
The fourth is the disease invading stage. From mid-to-late March to early April, the disease infects the stems after the jointing of the wheat plants to form flower stems.
The fifth is the performance period of the white ear. The stalks of the seriously ill strains showed white spikes at the end of April and early May, especially after the rain, and they continued to have a hot and dry weather. The dry and white ears showed faster. Warm autumn and winter, spring rainy and humid weather is conducive to the disease; spring is cold, cold damage, heavy disease; large amount of nitrogen fertilizer, heavy disease; early sowing, large amount of seeds, large amount of growth before winter, early infection, heavy disease after winter The grass is heavy and the disease is heavy; the terrain is low and the disease is heavy.
Second, the symptoms of harm
After wheat is infected by sheath blight, there are symptoms such as rotten buds, dead seedlings, stalks of stems, and white spikes of plants in various growth stages. The symptoms mainly appear on the sheath and stem. In the early stage of the disease, yellow-brown oval or fusiform lesions are produced on the leaf sheath of the near surface. Later, the diseased part gradually expands, the color becomes darker, and the inward development develops the damage to the stem. In severe cases, the early death occurs, and the later stage of the wheat appears to be white. ear. Significant symptoms began to appear in the three-leaf to four-leaf stage of wheat. Before and after jointing, sheath blight mainly harmed wheat sheath and stem, and the symptoms were clearly manifested. In the middle and late stages of wheat growth, the fusiform lesions on the leaf sheath are combined into a cloud-like shape with a pale yellow color in the middle, and there is a clear tan loop around the lesion. The lesion can extend up the leaf sheath to the flag leaf, forming a yellow-brown flower stalk. On the surface of the diseased plant, the surface of the leaf sheath lesions produces white mold hyphae, which are entangled into a mass. Finally, a large number of scattered, nearly spherical brown particles, ie, sclerotia, can be formed. Damage to stems can easily cause the diseased plants to fall, forming dead ears or dead white ears. The bases of the seriously ill plants become black and even rot. In the spring from mid-February to early April, the temperature increased, the spread of germs spread between wheat plants, and the rate of diseased plants increased rapidly. From early April to mid-May, with the elongation of the base of the plant and the spread of pathogens, the disease index The surge has increased rapidly. At this time, the lesions in the stalk and the stalk are rapidly expanding, the tiller is dead, and the disease index is upgraded, which becomes another peak period of the infection of wheat sheath blight.
Third, prevention measures
1. Master the reasonable sowing date. Avoid sowing too early, prevent premature winter long; fine sowing, do evenly spread, promote strong wintering. Conditional use of machine broadcast technology to reduce the occurrence of diseases. Strictly control the reasonable amount of seeding. Practice shows that the general seeding amount is large, and the late wheat group is easy to be too large. If it encounters a rainy year, the field humidity is high, which is very conducive to the occurrence of field sheath blight.
2. Add organic fertilizer. Formulated fertilization technology, rational application of NPK fertilizer. Nitrogen fertilizer should not be applied or applied excessively to control the excessive growth of wheat, promote the development of wheat roots and enhance its disease resistance. Adding organic fertilizer is an effective measure to promote the stable growth of wheat and improve disease resistance. However, it should be noted that manure with diseased bodies must be fertilized by high temperature before application, preventing a large number of bacterial sources from being brought into the field and becoming an effective source of infection.
3. Manage water properly. After entering the spring, strengthen the management of fertilizer and water, do a good job in the ditch system, and drain irrigation. After the rain, it can eliminate the water in the field and keep the soil in the wheat field dry. After the wheat is green, it is poured early and lightly poured into the green water. Do not flood the water to avoid excessive long-term humidity between the plants. Timely removal of weeds in the field, timely drainage after rain, has a good effect on controlling field sheath blight. When the spring cold wave comes, it depends on the watering of the sky to minimize the impact of low temperature and cold damage.
4. Chemical control. The use of pesticides to control wheat sheath blight is still an indispensable means of prevention and control, and we must pay close attention to it. In the past, when the prevention and control of wheat sheath blight was carried out, the effect of drug control was poor. According to the analysis, there were the following reasons: First, the treatment of seeds was not thorough, and the production did not reach the requirement that the seeds were not coated (not treated). . Second, the spring prevention is late. Late glutinous wheat is generally sown in the middle and late October. After the emergence of wheat, the pathogens infect the seedlings, forming a peak of infection, but the damage is not obvious, and production is easy to ignore. In the following year, wheat grows green, and the bacteria gradually infect and multiply. The common prevention and control time in production is from late March to early April, and the time is late. At this time, the sheath blight spreads rapidly, and the wheat plant type is large, the waste liquid is wasted, and the control effect is greatly affected. Third, the liquid medicine is generally insufficient. The liquid can not fully wet the stems and leaves of the wheat base, greatly reducing the control effect. Into the spring to control wheat sheath blight, should pay attention to the prevention and treatment of drugs: First, select the drug. In the early spring wheat returning to the jointing stage, the first dose of the drug is sprayed before the pathogen begins to enter the stem and the diseased plant rate reaches 10%. Can use 16% Jinggangmycin soluble powder 50~60g per acre, or 5% Jinggangmycin water 300~400ml, or 10% Jinggang·Bacillus suspending agent 250~300ml, or 25% propiconazole 30~40 ml of emulsifiable concentrate, or 15~20 ml of 10% hexaconazole suspension, or 20~30 ml of 30% benzyl-propiconazole emulsifiable concentrate. The second is to increase the amount of liquid. After selecting the correcting agent, it is required to spray 60-75 kg of water per acre, and the liquid should be sprayed into the base of the wheat stem and the root soil. If the prevention time is postponed, the amount of liquid medicine should be increased. It is required to use 75~100 kg of liquid per acre, and the diseased field will be prevented once again for 10~15 days. When applying dew in the morning, it is beneficial to spread the drug solution and flow to the base of the wheat plant to improve the control effect.
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