There are several types of tobacco virus diseases and how to prevent them.

Tobacco virus disease is widespread in various tobacco-growing areas in China, and its harm is serious in some areas, which directly affects the yield and quality of tobacco leaves to some extent. In China's tobacco-growing areas, common mosaic virus disease, cucumber mosaic virus disease, potato Y virus disease and etching virus disease are the main hazards. It is of great significance to identify these four virus diseases and cooperate with reasonable prevention and control measures for tobacco production. 1 main symptoms of virus disease 1. 1 common mosaic virus disease occurs in tobacco seedling stage and field stage, especially in April-July. At the early stage of tobacco disease, the color of veins and adjacent mesophyll tissues became pale and translucent, and then the leaves appeared thick green or yellow-green "mosaic" with uneven thickness. The leaves of seriously ill plants withered, the heart leaves twisted, the plants were short and grew slowly. At the early stage of 1.2, the leaves of tobacco plants with cucumber mosaic virus were transparent, and dark green and light green leaves appeared a few days later. The leaves often become narrow, thin and twisted, the leaf base is elongated, the surface hair falls off and loses its luster, and the leaf edge turns up. Brown necrotic spots or dark brown lightning necrotic spots along the main lateral veins appeared in the middle and lower leaves of some diseased plants. The typical mosaic leaves of cucumber show large and obvious bubble spots, forming a large area of losing green and a large area of dark green. 1.3 The symptoms of potato Y virus disease can be divided into two categories, one is mottled mosaic system, and the tissues on both sides of veins are dark green banded spots, which is called "vein zone". The other is vein necrosis, which often extends to the middle vein and even enters the vascular tissue and pith of the stem, leading to the death of the whole plant. Sometimes brown or white necrotic spots appear on the leaves. After the necrotic spots are connected into pieces, the whole leaves are "burning spots". In the field, PVY often forms a compound infection with TMV, CMV and TEV, which aggravates the harm. The symptoms of tobacco plants affected by 1.4 etching virus disease generally appear in the middle and late stage of vigorous growth, and leaf necrosis disease mostly spreads from bottom to top in the lower two sheds. At the beginning of the disease, chlorosis and yellow spots are formed on the leaves, and then spread along the veinlets, connecting brown or white linear spots. In severe cases, the lesion covers the whole leaf surface. In the later stage, the diseased tissue died and fell off, leaving only the skeleton of the main and lateral veins. At present, there is still no good single control measure for comprehensive prevention and treatment of tobacco virus diseases, and there is also a lack of effective treatment methods after the onset. Therefore, the prevention and treatment of virus diseases should focus on prevention, and a series of measures should be taken to reduce virus infection or cut off infection routes to improve tobacco disease resistance. 2. 1 chemical control 2. 1. 1 antiviral drugs were applied at seedling stage 1-2 times, before transplanting 1 time, and 96% of daptomycin was sprayed 3000 times +2 16544 days. At the early growth stage after transplanting, 265,438+065,438+06 tobacco-specific 600-fold solution was applied, 2-3 times a day. At present, the antiviral agents used in production are: Tianda Yufeng, Dongwang Du Xiao 900 times solution, Bike 500-800 times solution, Ke Jun Duke 250 times solution, etc. Tianda 2 1 16 special tobacco 600 times solution+Tianda Yufeng 1500 times solution has the best effect. 2. 1.2 Tobacco fields with aphid killing agents should be sprayed with insecticides in time to kill aphids, and 3% acetamiprid 1500 times or 2,000-3,000 times or 40% omethoate1500-2,000 times or at the peak of aphid migration to tobacco fields and the occurrence stage of aphid spots in fields. Alternate or mixed application, one or more times, spraying 1 time every 7- 15d, spraying evenly and fully. For details, please refer to this website: /bbs/viewthread.php? tid = 97 & ampextra=page%3D 1