How to prevent and cure tobacco red spot?

Tobacco red spot is a disease caused by fungi. Tobacco farmers in China are commonly known as erythema, root tiger eye, fire bubble spot and so on, which are the main leaf spot diseases in the mature period of tobacco leaves, which occur in all tobacco areas in our country, which not only makes the tobacco leaves incomplete and the grade down, but also makes the taste worse and reduces the industrial use value due to the disharmony of inherent quality. let's take a look at how to prevent tobacco red spot disease.

Symptoms of tobacco red spot disease

In the middle and later stage of the field, disease spots began to appear in the lower leaves of tobacco plants, which were yellow-brown round dots at the beginning, and then expanded to 1cm. The disease spots were round or irregular round, and there were yellow halos around the disease spots. Above produced obvious disease spots: the center as the center of the concentric wheel pattern, brittle, easy to break. When the air is moist, dark brown or dark brown mildew is produced on the disease spot, that is, the conidiophores and conidia of the pathogen (the basis of field diagnosis). When the weather is dry, the center of the spot is often broken, which is easy to produce perforation. In severe cases, the disease spots can meet each other to form large disease spots, and break off. When the main vein, pedicel, capsule and stem are infected by the pathogen, smaller dark brown or black spots can be produced. Near harvest, the stem produces round or nearly round dark brown sunken spots.

Incidence regularity of tobacco brown spot

The hyphae overwintered on the diseased body, and when the conditions were suitable the next year, conidia were produced and spread by wind and rain. Planting resistant and susceptible varieties in a large area, it is easy to cause epidemic in tobacco fields with concentrated overcast and rain, high nitrogen application, high planting density and poor ventilation and light transmission in the mature period (July to August).

Agricultural control of tobacco brown spot disease

1. Select resistant (tolerant) varieties: resistant varieties include Zhongyan 98 and so on. The moderately resistant varieties are Yunyan 85, K326Jing RGll, G28, K346 and so on. RGl7 and Zhongyan 9203 also have certain disease resistance.

2. Increase the application of organic fertilizer: properly increase the application of organic fertilizer and cake fertilizer, control the amount of nitrogen fertilizer, strengthen field management, and improve the disease resistance of tobacco plants.

3. Reasonable close planting: especially in the areas with serious disease, it is required that the adult plant should not be closed, the continuous area should be moderate, and it should not be too large to avoid the disease being difficult to control once the disease is prevalent.

4. Timely topping harvest: the topping time is determined according to soil fertility and variety. If the top is topped too early, the upper leaves grow too large, the tobacco plants are often umbrella-shaped, and the lower leaves are poorly ventilated and transparent, so they are vulnerable to bacteria. Timely harvesting of mature tobacco leaves can prevent and control the occurrence and spread of diseases and reduce the harm.

5. Rational rotation: the rotation system has been implemented for more than 2 years.

Chemical control of tobacco brown spot

1. When the bottom leaves are harvested for the first time, 40% sclerotia net wettable powder 400 × 500 times can be sprayed, 50 ~ 7s kg per mu, once every 10 days, 2 times continuously for 3 times, the control effect is better.

2. 1.5% polyantimycin 100 times or 0.3% Koshengmycin 200 times solution can be used for foliar spraying in the budding stage of tobacco plants, 50 to 75 kg per mu, and applied again half a month later, the control effect is better.

3. 10% Polaroid wettable powder 800-1000 times solution can be used at the initial stage of the disease, once every 7-10 days for 2-3 consecutive times. Or spray control with 30% acrylic suspension 600 times 800 times, or 47% Baofengning wettable powder 600 times 900 times, 50 kilograms per mu, once every 7 days, a total of 2 times 3 times, the control effect is better.

4. In the tobacco field with mixed occurrence of red spot disease and wildfire disease, 45% Jinyeshu wettable powder 500: 600 times liquid spray, once every 7 days, a total of 2 times, the control effect is better.