Tobacco Blight

Symptoms have occurred in Zhejiang, Fujian, Guangdong, Guangxi, Guizhou, Hunan, and Taiwan. In recent years, Henan, Shaanxi, Shandong, and Liaoning have also been discovered. At the onset of the disease, the diseased plants withered to one side, and the roots of the diseased side became black and rot. Some of them firstly produce lesions in the leaves of the leaf veins, and there are long black streaks on the stems. Some of the streaks spread to the top of the diseased plants or withered petioles. In the middle stage of disease, all the leaves wilted, the stripe surface became black and rot, the roots also turned black and rotted, the stems forcedly pressed the incision, and yellow-white bacilli were spilled from the catheter. The stems and veins of the diseased plants became dark. The pathogenic bacteria invaded into the pith, and the pulpy part of the stem was honeycombed or rotted to form a cavity, leaving only the xylem.

Pathogen Pseudomonas solanacearum (E.F. Smith) Smith called Pseudomonas alba, a bacterium. Rod-shaped, round at both ends, size 0.9-20.5-0.8 (um), 1-3 flagellum, multi unipolar, non-deciduous, Gram-negative, aerogenic . The temperature limit for the growth of pathogenic bacteria is 18-37°C, and 30-35°C is the most suitable. Lethal at 52°C for 10 minutes. Optimum pH 6.6. The strain has identified 5 races and 5 biotypes. The strains infecting tobacco are race 1 and biotypes I, III, and IV. Under natural conditions, biotypes often change.

Transmission routes and pathogenic conditions Pathogenic bacteria can survive for up to 7 months in diseased bodies and the pathogens either fall into the soil or overwinter in compost. The survival time of the bacteria in different soils varies greatly. Some are very short and some are as long as 25 years. The bacteria invade from the root wound and produce extracellular polysaccharides (EPS), forming a gelatinous layer outside the bacteria, blocking the membranous porcine membrane, and causing the diseased plants to wilt. In addition, polygalacturonase can cause diseased tissue browning. After the bacteria enter the vascular bundle, they secrete pectinase and dissolve the adhesive layer in the host cells, causing the host's cortex and pith tissue to rot and die, and forming a cavity at the base of the stem. In the field, germs are transmitted by irrigation water and rain, as well as humans and animals. The incidence in southern China is heavier. There are differences in disease resistance among varieties.

Control methods (1) Selection of varieties resistant to bacterial wilt in accordance with local conditions such as Xia Kang 1, Xia Kang 3, Cokerl76, Va707, Va770, Nc89, Nc2326, Taiwan Tobacco, Lettering 101, G80, TT6, K394, C411, Bell 93, Lamson, Kirk 316, Kirk 319 and so on. (2) More than 3 years of rotation with grass crops. (3) early sowing and early planting, the peak incidence of escape from the rainy season can reduce the damage. (4) Advocate the use of compost that is fermented by enzymes, and do not use fertilizers from diseased plants. Pay attention to adding boron fertilizer. Nitrogen fertilizer promotes the use of nitrate nitrogen instead of ammonia nitrogen. (5) To strengthen management, Tian asked the diseased plant to remove the diseased point after quick removal. The use of sorghum cultivation, timely drainage after the rain, to prevent moisture retention. (6) In the initial stage of disease, spraying or irrigating the streptomycin sulfate 4000 times solution or 14% collaborative ammonia bronze solution 300 times, 77% killing the particulate wettable powder 600 times, 47% Garethon WP 700 800 times liquid. When irrigating the roots, each plant used 400-500m1 of good liquid, every 10 days, and irrigation for 2-3 times.