Symptoms of symptoms appear at the beginning of the Ming dynasty, after the performance of the leaves in the new leaves, leaves narrowing, stretching was tight, thin leaves hair, loss of luster. Some diseased leaves form dark green and white mosaic leaves, which are ecchymosis; some leaf margins curl upward; some leaves are yellow mottled; some veins are lightning-like necrosis, some plants are dwarf yellow; some diseased leaves are rough, hair Brittleness, elongation of the base of the leaf, narrowing and thinning of the mesophyll tissue on both sides, slenderness of the leaf tip, symptoms of the disease due to different breeds, and different growth stages.
The pathogen Cucumber mosaic virus is called cucumber mosaic virus, abbreviated as CMV, and is a virus. The virion is a spherical, icosahedron with a size of 28-30 nm. Most of the CMV strains were inactivated at 65-70°C for 10 minutes and the dilution limit was 100,000 times. The survival time at room temperature was 72-96 hours in vitro. The CMV strains on tobacco include: typical symptoms (D), mild (G), macular (Yl and Yz), twisted (SD), and necrotic (TN) lines.
Transmission routes and disease conditions CMV can be transmitted through aphids and friction. There are more than 60 species of aphids that can spread the virus. Tobacco fields mainly include haze and cotton aphids. CMV proliferates and metastasizes rapidly in tobacco plants. It appears in mesophyll cells at 24°C for 6 hours after infestation, and can re-infect for 48 hours. The disease can be manifested after 4 days. CMV can infect approximately 36 species of 36 dicotyledonous plants and 4 family of monocotyledonous plants. It is not possible to overwinter on the sick and disabled body, mainly on wintering vegetables, perennial trees, and farmland weeds. Hunchun was transferred to the tobacco plant through the winged pelicans. The aphid spreads the virus in a non-persistent way. The virus can be obtained by smoking on the diseased plant for 2 minutes. The smoking process can be completed on the healthy plant for 15 to 120 seconds. Flue-cured tobacco plants were more susceptible during the prolonged bud stage and increased resistance after budding. Tobacco fields adjacent to vegetables such as cucumbers, tomatoes, bell peppers, etc., are more likely to become diseased when there are more locusts. About 10 days after the field locusts entered the peak of migration, high incidence of bees began to appear. The winter and early spring temperatures are low, the amount of snowfall is large, the number of overwintering mites is small, and early spring activities are late; CMV is light. If Yuchun is relatively dry, there will be large fluctuations in temperature before the prosperous period, and there will be dry hot winds, which can lead to a CMV pandemic. There are more rainy days, relatively high relative humidity, fewer locust occurrences, and less CMV.
Control methods (1) Breeding resistant varieties such as genetically engineered tobacco Nc89, G80, Taiwanese TT6, TT7, and other disease-resistant Zhongyou 14 and so on. (2) According to the local climatic conditions, adjust the transplanting period according to local conditions and avoid the peak period of aphid migration. Apply base fertilizer and use formula fertilization technology to avoid partial application of nitrogen fertilizer. Tobacco fields are as far away as possible from the Solanaceae vegetable field and the melon field. Remove weeds and poisonous plants in time. (3) Implement agricultural protection measures centered on tobacco and wheat intercropping. According to the yellowish nature of the locust, the haze first flies to the wheat and sucks off the virus in the mouthparts, thereby reducing the opportunity for transmission of the virus and avoiding the sensational period of the tobacco. For example, spraying the anti-caries medicine on wheat has better effect. Henan's successful model is a line of Mai Yi Lung or a second line of Maiyi Lung. Silver gray film can also be used to avoid defects. (4) Actively curb lice and prevent disease. Timely spraying on tobacco seedbeds and fields will reduce the spread and spread of CMV. See smoke abattoir for prevention methods. (5) Chemical control See Tobacco Mosaic Disease.
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