Corn brown spot disease is a fungal disease that has been discovered in recent years and is a serious fungal disease. There are two main causes of this disease: First, the weather conditions of high temperature and high humidity, especially in the face of continuous rainfall, the incidence of the disease increased; Second, farmers often only pay attention to nitrogen fertilizer when fertilizing, ignore phosphorus, potassium fertilizer The application of phosphorus, potassium caused by the lack of corn plants, plants can easily occur brown spot. This disease has a great impact on the yield of corn. Failure to take measures in the early stages of corn growth will eventually lead to corn crop failure; the onset of corn ear in the middle period will cause a significant reduction in corn production; in the late stages, symptoms of grain insufficiency will occur. In order to prevent such diseases from causing losses to farmers' friends, we will introduce corn brown spot disease:
First, the symptoms:
It mainly occurs on corn leaves, leaf sheaths and stems. Occurs at the tip of the top leaflet, initially light yellow, gradually turning into yellowish-brown or dark brown spots. The lesions are round or elliptical. In severe cases, several or even all the lesions are covered with spots on leaf sheaths. Large brown spots appear on veins and veins. The surface of the lesions at the late stage of the disease is ruptured and the leaf cell tissue is necrotic. Brown powder (sporangia of pathogenic bacteria) is scattered, and the diseased leaves are partially spalled. The veins and vascular bundles remain as filaments. Finally, the leaves retreated green and yellow, dry, and severely caused the plants to die. The lesions on stems occurred in the vicinity of the festival, and the wind easily collapsed.
Second, the incidence of the law: germs with dormant sporangia in the sick or wintering in the soil. The spores produced in the following year are transmitted to the leaves through wind and rain, and the high temperature and humidity in July to August are conducive to disease. In general, low-lying plots, heavy plots, and poorly ventilated plots are heavier.
Third, the cause of the disease
1. There are brown spot pathogens in the soil and in the diseased body tissues; firstly, when high sensitive varieties are continuously cropped, the amount of bacteria in the soil will increase by 5 to 10 times per year; secondly, in the aspect of fertilization, straws with diseased residues will be returned to the field. , The application of uncooked manure compost or bacterial farm manure brought the pathogens into the field, resulting in a corresponding increase in the number of bacteria.
2, 5-8 corn leaves, soil fertility is not enough, yellow corn leaf color, emergence of de-fertilizer, corn disease resistance is reduced, is the main cause of brown spot disease.
3, high air temperature, high humidity.
Fourth, control methods:
1. Agricultural Measures (1) After the corn is harvested, the diseased body should be completely removed and the soil should be deeply plowed. Apply enough base fertilizer and timely fertilizer. Generally, 4 to 5 leaves of maize should be applied to the seedlings, that is, nitrogen, phosphorus and potassium compound fertilizers 10 to 15 kg/mu. Pay attention to the combination of nitrogen, phosphorus, and potassium fertilizers. At the same time as reasonably applying fertilizer, timely watering and timely cultivating and weeding can promote the healthy growth of corn, enhance disease resistance, and eliminate the host and reduce disease. (2) Select disease-resistant varieties and implement rotation for more than 3 years; (3) Suitable planting density. Planting density should be appropriate, do not arbitrarily increase the density, to increase field permeability; vigorously promote dry sowing and formula fertilization techniques, dry sowing can make corn in the seedling period to exercise, rooted, deep root, seedling strong. Formula fertilization, increasing N, P, and K fertilizers to make maize plants robust, rapid, and enhance disease resistance
2 Chemical control (1) Early prevention. In the 4 to 5 leaf stage of maize, spraying 25% triadimefon 1500 times foliar spray per acre can prevent the occurrence of corn brown spot. (2) timely prevention and treatment. Immediately after the onset of corn, spray 25% of triadimefon(triazole copper) wettable powder 1500 times on the stems and leaves or use fungicides to spray. In order to improve the prevention and control effect, some foliar treasures, potassium dihydrogen phosphate, urea, etc. can be properly added in the liquid medicine. Combining with topdressing available fertilizers, the spread of diseases can be controlled, and the robustness of corn can be promoted to improve the disease resistance of corn. According to the current rainy weather characteristics, spraying bactericide should be 2 to 3 times, 7 days apart, within 6 hours after spraying, rain should be added after the rain. Maximize the control of corn brown spot. In addition, the application time should be before 10 o'clock in the morning, after 4 o'clock in the afternoon, to avoid the application of high temperature time.
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