Tobacco frog eye disease, also known as white spot disease and snake eye disease in different regions, is a leaf disease that is caused by fungi and commonly occurs in the mature leaf collection period of tobacco, and occurs in various tobacco producing areas. The occurrence of frog eye disease in tobacco, if not prevented, can cause a decline in tobacco yield and quality.
The main symptoms. The frog eye disease mainly occurs on adult plants in the field, and it also has disease at the seedling stage. The disease spot is slightly smaller than the disease, round, brown, brown or dirty gray, 2 to 15 mm in diameter, the center is white, narrow and narrow, dark brown, shaped like a frog eye, hence the name "frog eye disease." The lesions are occasionally angular and have no white centers. There is a gray mold in the center of the lesion. The lesions mostly occurred on the lower leaves, and the young leaves were more resistant than the mature ones. After the bacteria are activated, they spread from bottom to top in sequence, and young leaves are also infested. There can be hundreds of lesions on a blade, and even countless. In the event of a storm, the lesions often break off and become perforated. When severe, many lesions form a continuum, causing the entire leaf to die. Before the harvest, the tobacco leaves are infected by the bacteria. After baking, “green spots†or “dark spots†of different sizes appear, affecting the quality of tobacco leaves.
Occurrence characteristics. The frog ophthalmophilus pathogen mainly overwintered with mycelium on the residue of soil disease, and infected the tobacco seedling the following spring. The diseased seedlings were planted in Daejeon and became the main source of Daejeon's germs. The conidiospores produced in the lesions of the year can be caused by wind and rain to cause other diseases. The lower leaves first became diseased and gradually expanded to the upper part, causing an epidemic. During the harvest season, when the temperature reaches 10 to 34°C, the disease is severe if there is continuous rain or high humidity in the field. The terrain is low, the soil is heavy, the drainage is poor, the tobacco plants are too dense, and the disease in the late tobacco field is heavy. Leaves damaged by mosaic disease are prone to frog eye disease. Before harvesting, the leaves infected by pathogens but not presenting symptoms will continue to develop when the baking room temperature is between 30 and 32°C, resulting in green spots or dark spots.
Prevention methods. Frog eye disease is an airborne disease with a wide range of hosts, and most of the species currently produced are susceptible to disease. Therefore, active and effective comprehensive prevention and control methods should be adopted for prevention and control. (1) Implement rotation. The best conditions to implement the tobacco, rice rotation system, the implementation of ground tobacco and corn, sorghum, sweet potato 2 to 3 years of rotation. (2) After the tobacco is harvested, the field tobacco plants and residues are removed, and the deep plowing will turn the bacteria into the deep layer of the soil to reduce the damage in the coming year. (3) appropriate early planting, reasonable planting. The planting density is about 1200 per mu, so that the plants can be ventilated and lighted, and the disease conditions can be controlled. (4) Science and balanced fertilization ensure that the three elements of nitrogen, phosphorus, and potassium are properly coordinated to promote robust growth of plants and increase their physiological resistance. (5) timely removal of diseased leaves to reduce disease development and spread. (6) Early prevention with Pharmacy, regular injection of Bordeaux or 80% Zeoxin 500 times for prevention at the seedling stage. In the early stage of the disease, Daejeon used a 1:1:150 fold Bordeaux mixture, or 40% Spermide 400 times solution, or 40% Carbendazim 500 times solution, or 80% Sensen Zinc 500 times, or 75% chlorothalonil solution. 800 times liquid, or 20% triadimefon 1000 times and other alternate spray, spray once every 7 days, depending on the condition even spray 2 or 3 times.
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