Due to the high temperature, high humidity, and low rainfall during the summer, the occurrence of smut in some corn fields in the city has become common and has become one of the major diseases in corn production. According to the author's recent investigation, combined with years of work experience, the following points are made on the causes of corn smut and how to prevent it. Pharmaceutical Glass Vial, Pharmaceutical Vial, Pharma Glass Vial, Pharma Vial Pharmaceutical Glass Vial Pharmaceutical Glass Vial,Pharmaceutical Vial,Pharma Glass Vial,Pharma Vial China Lemon Trading Co.,Ltd , https://www.lemonvial.com
1 smut symptoms Corn smut disease, also known as tumor black powder, commonly known as "black egg head", is a local invasive disease, infection for a long time, corn seedling to maturity can infect. Tassels, ears, aerial roots, stems, leaves, sheaths, axillary buds and other parts of the corn can produce tumors, but the shapes and sizes vary greatly. Tumors are nearly spherical, angular, rod-shaped, or irregular, some are solitary, some are clustered or stacked, and they vary in size. The appearance of the tumor is a white, off-white film. The inside is tender, white, soft and juicey, and turns gray and black when mature. In general, a corn can produce multiple tumors. At the onset of seedling stage, small nodules are formed on the base of the stem near the ground or on the back of the leaves, and blackish aneurysms in the base of the stem expand more. When severe, the seedlings may die. Plant diseases are most seriously affected by the occurrence of the ear disease. When the disease occurs, the upper half or individual grains of the ear produce nodular bacillary dysentery. In severe cases, the whole ear forms malformed bacillary dysentery. At the beginning, it is white, after which the gradient is gray, and the latter is white. The gray to dark gray film, after the film ruptures, emits black-gray powder (ie, teliospores), and the teliospores can germinate immediately and undergo reinfection.
2 Occurrences The smut fungus is a subgenus of the genus Basidiomycetes. The black powder that is emitted from the diseased part is the winter spore of the pathogen. It is spherical or ovate and winters on the field soil, surface, diseased plants and seeds. The teliospores do not have a dormant period and germination can occur if the conditions are suitable. The smut disease is dominated by soil and seed-borne disease. The epidemic of the disease is affected by the number of bacteria in the winter, the environmental conditions, and disease resistance of the varieties.
2.1 Climatic conditions. High temperature and high humidity are favorable for the germination of teliospores, and the temperature from the seedlings to the silking stage is consistent with the optimum temperature of teliospore germination, resulting in the epidemic of disease. Maize is affected by drought, especially drought before young panicle differentiation, plant resistance to disease declines, and at the same time due to the inability to quickly pass through the stage of maturity and extend the period of disease. Therefore, the wet and high-temperature climate after the drought is the main reason for the disease. In addition, storms or hail can cause a great deal of mechanical damage and aggravate the disease. The city is dominated by summer corn, which is generally hot and dry during the past two years in summer. According to the survey, the year of dry weather is heavy in areas that are not irrigated.
2.2 Cultivation conditions. After years of continuous cropping, a large number of pathogens have accumulated and the disease has become severe. In drought-sparing areas, the residual fungal winter spores in the field are prone to survive in sandy soils lacking organic matter. In the following year, the amount of newly infected bacteria is large and the incidence is often heavier. In wet areas or irrigated areas, it is rich in moisture. In organic soils, the pathogenic teliospores are easy to germinate or are susceptible to death from other microorganisms, and their incidence is often light. Therefore, the northern corn area is heavier than the southern corn.
2.3 Number of bacteria sources The cultivation system of the city is dominated by wheat-maize cultivation. The continuous cropping phenomenon is very serious. In some places up to ten years, planting varieties with poor resistance to black smut, due to a large number of diseases, germs scattered in the fields, resulting in soil A lot of bacteria accumulated. In addition, due to farmers' growing habits, it is easy to grow the same variety for many years, which is also easy to cause the accumulation of bacteria, once the environmental conditions are suitable, it is prone to large-scale infection. The main reasons for the large amount of residual bacteria in the field are the expansion of the application of corn stalk return and no-tillage technology, or the inability to timely treat manure-bearing farmyard manure and crop residues.
2.4 Corn Varieties Resistance to corn smut was one of the major diseases of corn in China before the mid-1970s. It was extremely common. In 1997, some counties in Hebei Province took place. There were 174,000 mu in Jinzhou, accounting for 58.4% of the sown area of ​​corn, 3.8% of the diseased plants in general, and more than 15% of individual varieties. According to the survey, corn varieties such as Ludan 9066, Saitama 68, Jingke 8, Jingke 11, Zhengdan 958, Zhengdan 951, Qingya 4 and Saitama 3 were severely affected this year, and the general disease strains 5-10 %, up to 90% (Zhengdan 958), causing fulminant pandemic in some areas, indicating that variety resistance is an important factor in the occurrence of smut.
3 Comprehensive prevention and control measures
3.1 Planting disease-resistant varieties for planting disease-resistant varieties is the most economical and effective method of prevention and control. It is also a problem that smut prevention and control must solve. At the same time, combining the occurrence characteristics of smut, do a good job in guide the distribution of varieties, in the hard-hit areas of smut Actively promote disease-resistant varieties and compress or rank susceptible varieties as soon as possible. As a breeding unit, the identification of anti-aridenic materials and varieties should be strengthened.
3.2 Reduce bacteria source
3.2.1 Adaptation to local conditions and rational rotation: Crop rotation is an effective measure to reduce the amount of bacteria in the field. From the perspective of the incidence of smut in our city, the incidence of continuous cropping is severe, and the disease incidence in the crop rotation is obviously lighter. Therefore, the actual situation in each region is based on reasonable rotation. Avoid continuous multi-year operations. According to the characteristics of pathogens surviving in the soil for more than two years, a three-year rotation cycle can be used. Variety rotation can also play a preventive role, avoiding planting the same species for many years in the same plot.
3.2.2 Control of Chemicals: Seed-borne bacteria are the main source of infection for smut, especially for long-distance transmission. Seed dressing or seed dressing can not only inhibit the pathogenic bacteria that the seeds carry, but also have some preventive and control effects on the germination of the seeds. There are many types of coating agents and seed dressings currently used in production and application. Drugs with strong systemic absorption and long residual period of efficacy should be selected. For example, for every 50 kg of corn seed, 25% triadimefon 200 g or 12.5% ​​speed poly 1000 g can also be used. Seed weight of 0.5% of 50% thiram or mu with 2% tebuconazole wet and dry mix 10 g seed dressing.
3.3 Strengthen field management, avoid timely inoculation of multiple infestations, appropriate depth and depth of sowing, promote early-onset seedling growth, and reduce the chance of infection. Closely plant the plant, cultivate strong seedlings, and enhance the resistance of the variety. Strengthen the management of fertilizer and water, pay attention to the application of nitrogen, phosphorus and potassium to avoid partial application of nitrogen fertilizer. Irrigation should be timely, especially before and after tasseling, to ensure water supply. In the early stage of disease or after detasseling, the pathogenic bacteria “tumor†at the site of the disease should be manually removed, and the bacteria should be removed early in the period and be carried out outside the field for deeper incineration or incineration to reduce the amount of bacteria in the field. Must not be random, still unwitting. To reduce the re-infectious bacteria source in the year and the source of bacteria in the following year.