There are no specific drugs for how to prevent silk smut in corn planting in 2017. Corn smut is also known as Umi and dumb corn, which is common in North China, Northeast China, Central China, Southwest China, South China and Northwest China. Since the disease was first reported in Northeast China in 1919, it has spread rapidly and has occurred to varying degrees every year. From the perspective of China, the incidence of the north spring corn area, the southwest hilly mountain corn area and the northwest corn area is heavier. In the general year, the incidence rate is between 2% and 8%, and the individual plots are 60% to 70%, and the losses are heavy. In the 1980s, corn smut was basically controlled, but it was still one of the main diseases of corn production. The typical disease of corn smut is the male flower morphing, the male flower base is swollen, and the inside is a pack of black powder, which cannot form tassel. Ears of the ear are shortened and the base is thick. Except for the leaves, the whole ear is a pack of black powder and scattered silk, which seriously affects the yield of corn. 1. Seedling symptoms of corn smut Maize head smut is a systemic invasive disease invading at the seedling stage. Typical symptoms are usually present at the ear stage, mainly affecting the ears and tassels. Plants with severe damage can exhibit various symptoms at the seedling stage. The seedlings increased in clusters, the plants were obviously dwarfed, the internodes were shortened, and the leaves were dark and green. The farmers said that the disease was: "the head is short, the leaves are dense, the lower side is thick, the upper side is fine, the leaves are dark, the color is green, the body is still There are bends. Some varieties have yellow-white streaks parallel to the veins on the leaves, and some of the seedlings are tightly rolled and twisted together. 2. Adult stage symptoms of corn smut Symptoms on the ear of corn in adult stage can be divided into two types, namely black ear and abnormal deformed ear. 1 black ear, smut ear, except for the sorghum leaf, the whole ear becomes a black powder bag, which is mixed with the filamentous host vascular bundle tissue, so it is called silk smut. The affected ear is short, the base is thick, the tip is sharp, and the shape is approximately spherical. 2 abnormal metamorphosis of the ear is due to the deformation of the tassel flower without forming stamens, and its glume is multi-lobed due to the stimulation of pathogenic bacteria; the female glume may also grow excessively into a tubular long thorn due to the stimulation of pathogens, which is a thorny head. The base of the long thorn is slightly thicker, the tip is slightly thinner, the center is loose, and the length is different. The base of the ear is clumped upwards, and the whole ear is deformed. The pathogen of corn smut is the pathogen of corn smut. The bacterium is winter spores in the soil, and some are mixed with manure or adhere to the surface of the seeds for winter. Soil-borne bacteria are the most important source of primary infection, and seed-borne bacteria are the main route for long-distance transmission of diseases. The teliospores can survive for 2 to 3 years in the soil. The teliospores begin to mature during the silking stage of the maize, and a large number of them fall into the soil, and some fall on the seeds (especially during the harvest). After sowing, the germ is generally infested when the seeds are germinated or the seedlings are just unearthed, and some are also infested at the 2nd to 3rd leaf stage (it is reported that the final stage of infection is 7-8 leaves). The germination of teliospores produces isolated sclerotium, which occurs as an invasive silk, invades from the germ or radicle, and quickly spreads to the stem and grows along the growth point. When the flower buds begin to differentiate, the hyphae enter the floral primitive, invade the ears and tassels, and finally destroy the male and female flowers. As the corn growth cone grows faster, the hyphae expands slowly and fails to enter the growth point of the stem of the plant, which causes some diseased plants to develop only in the ear and the tassel is disease-free. The bacteria overwinter on the soil, manure or seeds and become the source of infection at the beginning of the year. Seed carriers are the main route of long-distance transmission. The chlamydospores survive in the soil for 2 to 3 years. Invasion at the seedling stage is a systemic infection. When the corn is germinated after sowing, the wintering chlamydospores also begin to germinate. From the white tip to the 4th leaf stage of the corn, they can invade and reach the growth point. As the corn plants grow and develop, they enter the flower buds and ears, forming a large amount of black powder. , became silky black spikes, producing a large number of winter spores overwintering. The long-term and early-stage corn planting of maize has a serious incidence; the high-cold and cold-soil plot is prone to disease. The incidence of sandy soil is light. The dryness of the dry land is light and the incidence of sputum is heavy. Incidence condition of corn smut 1. The large-scale planting of susceptible varieties is one of the factors leading to the serious occurrence of silk smut. In addition, pathogens may develop new physiological races, resulting in loss of resistance to the original disease-resistant variety. 2. Long-term continuous cropping causes the soil to contain bacteria to increase rapidly. According to reports, if the bacterial strain is reflected by the disease rate, the amount of bacteria in the soil can increase by about 10 times per year. 3. Use unfertilized manure. According to the test, the incidence rate of the field of pig manure is 0.1%, and the incidence of field of dung-stained cow dung is as high as 17.4%-23%, and the incidence of field of cow dung is 10.6%~11.1%. 4. If the seed-borne bacteria are not sterilized and the residue of the diseased plant is not properly treated, the amount of bacteria in the soil will increase, resulting in serious occurrence of the disease. 5. The relationship between soil temperature, humidity and disease during the sowing of corn to emergence is extremely close. The soil temperature in the range of 15 ~ 30 ° C is conducive to the invasion of pathogens, the most suitable at 25 ° C. Too high or too low soil moisture is not conducive to the invasion of bacteria, the highest incidence in 20% humidity conditions. In addition, the higher the altitude, the deeper the sowing, and the weaker seed viability, the higher the incidence. Invasion temperature limit 15 ~ 35 ° C, suitable for infection temperature 20 ~ 30 ° C, 25 ° C optimum. A soil moisture content of less than 12% or more than 29% is unfavorable for its onset. Prevention and cure method of corn silk smut 1. Select excellent disease-resistant varieties The selection of resistant varieties is a fundamental measure to solve the disease. Generally, the parents are resistant to the disease, the hybrids are also resistant to the disease, the parents are susceptible, and the hybrids are also susceptible. Therefore, in the disease breeding work, excellent disease-resistant inbred lines should be selected as parents to obtain disease-resistant offspring. The disease-resistant hybrids include Danyu 13, Yandan 14, Yuyu 28 and the like. 2. Seed treatment before sowing Treating seeds with chemicals is an important part of comprehensive prevention and control. There are three methods of seed dressing and seed coating treatment. The path of infection of corn smut is seed, soil, and manure. In the seedling stage (before the five-leaf period), the bacteria in the soil can invade from the young shoots and the young roots. Therefore, it is necessary to select pesticides with strong systemic and long-lasting effects for the control of the medicament, and the effect is better. The triazole fungicide seed dressing has better effect on the control of corn silk smut, and the large-area control effect can be stabilized at 60%-70%. Promote the use of the following agents for seed treatment in production: 1 It is a more effective method to mix the seeds with powdery rust and hydroxy rusting with the active ingredient in the range of 0.2%-0.3% of the seed weight; 20% of rust and rust, 1 kilogram of water, 5 kilograms of water, 75 kilograms of corn, and 4 hours of boring effect well. 2 speed Poly is mixed with 100 kg of active ingredients and 100 kg of seeds. 3 Seed dressing with 0.3% oxygen ring slow release agent, the control effect can reach more than 90%. 4 Seed dressing with 50% carbendazim wettable powder at a seed weight of 0.3%-0.7%, or methyl thiophanate 50% wettable powder at a seed weight of 0.5%-0.7%. 5 Add 50 times of water with 50% chlormequat solution, soak seeds for 12h (hours), or mix with carbendazim and methyl thiophanate. 6 The choice of coated seeds also has a good control effect. 3, the removal of diseased plants Corn smut is mainly harmful to females and tassels, but it has been manifested in the seedling stage. With the increase of leaf age, the characteristics are more obvious, and the higher the diagnosis rate. The seedlings, the seedlings, the cultivating and weeding can be combined to remove the diseased seedlings and the suspicious seedlings, and the diseased plants are removed before the black powder of the germs is removed from the heading stage. The diseased plants to be removed should be buried and burned, and should not be thrown away in the field. 4. Strengthen farming and cultivation measures 1 Reasonable rotation: With crops such as sorghum, millet, soybean, sweet potato, etc., it will be rotated for more than 3 years. 2 Adjust the sowing date and improve the quality of sowing: the sowing date is suitable and the planting depth is consistent, and the thickness of the soil is suitable. 3 Removal of the diseased plants: Before the symptoms of the seedling stage and the growth period are obvious or the diseased ear is not cracked and the black powder (winter spores) is released, the diseased plants are removed in time and carried out in the field. 4 application of net fertilizer to reduce the amount of bacteria: it is forbidden to feed livestock and use fertilizer with diseased straw. Fertilizer should be fully decomposed and then applied to reduce the source of soil bacteria. In addition, clean the pastoral, handle the residue of the diseased plants in the field, and at the same time carry out deep lands in the autumn to reduce the source of the bacteria, thereby reducing the occurrence of diseases. ·Select resistant hybrids such as Danyu No.2, Danyu No.6, Danyu No.13, Zhongdan No.2, Jidan 101, Jidan 131, Sidan No.12, Liaodan No.2, Jindan No.6,本育9å·,掖å•11å·,掖å•13å·,é…’å•4å·,Shaandan No.9, Jingzao No.10, Zhongyu No.5, Jinxia No.7,冀å•29,冀å•30,é•¿æ—©No. 7, Fengyu No. 12, Liaodan No. 22, Longyuan 101, Haiyu No. 8, Haiyu No. 9, Xi Nong No. 11, Zhangdan 251, Nongda 3315, etc. · Implementing rotation for more than 3 years, adjusting the sowing date, improving the quality of sowing, appropriate late sowing, and adopting new techniques of mulching. Timely removal of new diseased plants and reduction of soil carriers. ·Pharmaceutical control with root coating agent coating corn before seeding according to the drug 1:40 for seed coating or with 10% diniconol EC 20g wet corn seed 100 kg, piled for 24 hours, control corn silk black Ear disease, better than triadimefon. It can also be used with seed dressing weight of 0.3%-0.4% triazolyl cream or 40% seed dressing double or 50% carbendazim wettable powder according to seed weight 0.7% seed dressing or 12.5% ​​speed Poly wettable powder for seed weight 0.2% seed dressing, this method needs to spray water to wet the seeds, then mix well with the powder and dry it to sow. In addition, 0.7% of 50% rust WP or 50% dexamethasone WP, 0.2% 50% thiram WP can be used for seed dressing. · The early removal of the diseased plant removes the diseased plant before the end of the rupture of the white film at the end of the disease. In particular, the plants of the late-pulling plant are inspected and examined several times, and the diseased plants are carried out of the field, buried or burned. Varieties or hybrids that exhibit symptoms at the seedling stage should be combined with the removal of the seedlings. To remove the diseased seedlings, it is necessary to insist on removing the disease from the "three customs", that is, the seedling stage, the strange seedlings, the suspicious seedlings; the diseased seedlings are removed before the jointing and tasseling; after the males are removed, the rats are removed, the wounds are thoroughly removed, and the diseased plants are carefully treated. To strengthen quarantine, all localities should make their own seeds. When they are planted in other places, they should conduct a survey of the place of origin to prevent the introduction of bacteria-borne seeds from the ward. 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