How to prevent and cure the latest tobacco red spot?

Tobacco brown spot disease is a disease caused by fungi, commonly known as red spot, root tiger eye, fire bubble spot, etc. in tobacco farmers in China, it is the main leaf spot disease in the mature period of tobacco leaves. All tobacco areas in China have occurred, which not only makes tobacco leaves incomplete and degraded, but also because of internal quality disharmony, makes taste worse and reduces the industrial use value. Let's take a look at how to control tobacco brown spot disease.

Symptoms of tobacco brown spot disease

At the middle and late stage of field, the disease spots began to appear on the lower leaves of tobacco plants, which were yellow brown round dots at the initial stage and expanded to 1~2 cm later. The disease spots were round or irregular, yellow halo circles were around the disease spots, and obvious concentric rings with the disease spots centered at the center were produced on the disease spots, which were brittle and easy to break. When the air is humid, dark brown or dark brown mold, i.e. conidia and conidia of the pathogen, is produced on the disease spots (the basis for field diagnosis). When the weather is dry, the center of the lesion often ruptures and is prone to perforation. Severe, the spots can meet each other to form large spots, and rupture off. When the main vein, pedicel, capsule and stem are infected by the fungus, they can produce small dark brown or black spots, and when they are close to harvest, the stems produce round or nearly round dark brown depressed spots.

Pathogenesis of tobacco brown spot disease

The mycelium overwinters on the diseased body, and when the conditions are suitable in the following year, conidia are produced and transmitted by wind and rain. A large area of resistant and susceptible varieties planted in mature period (July to August), concentrated rain, excessive nitrogen application, high planting density, poor ventilation and light transmission between tobacco fields, easy to cause human epidemic.

Agricultural Control of Tobacco Brown Spot Disease

1. Selection of disease-resistant (resistant) varieties: disease-resistant varieties include Zhongyan 98, etc. Yunyan 85, K326, RGl 1, G28, K346, RGl7 and Zhongyan 9203 were moderately resistant.

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

3. Reasonable close planting: especially in areas with serious disease, it is required that the rows are not closed at the adult stage, the contiguous area is moderate, and it is not too large to avoid the disease once it is popular and difficult to control.

4, timely topping harvest: according to soil fertility and varieties to determine the topping time. Topping too early, the upper leaves grow too large, tobacco plants often into umbrella-shaped, lower leaves ventilation and poor light transmission, vulnerable to the harm of germs. Timely harvest of mature tobacco leaves can prevent and control the occurrence and spread of diseases and reduce harm.

5. Reasonable rotation: implement rotation system for more than 2 years.

Chemical Control of Tobacco Brown Spot

1. When harvesting the bottom leaves for the first time, spray 400~500 times solution of 40% clerotium wettable powder, 50~7S kg solution per mu, once every 10 days, for 2~3 times continuously, and the control effect is better.

2, tobacco budding stage can be used 1.5% multi-antibiotic 100 times, or 0.3% cosamycin 200 times solution for foliar spray, 50~75 kg solution per mu, half a month later again, the control effect is better.

3. At the beginning of the disease, 800~1000 times solution of 10% Polian wettable powder can be used once every 7~10 days for 2~3 consecutive times. or spraying 600~800 times of 30% Dakeli suspension or 600~900 times of 47% Baofengning WP, 50~75 kg/mu, once every 7~10 days, spraying 2~3 times in total, the control effect is better.

4. In tobacco fields where brown spot disease and wildfire disease occur together, 45% Jinyeshu WP 500~600 times solution can be sprayed once 7~10 days for 2 times, and the control effect is better.