Identification and prevention of viral diseases

Virus disease is a special disease, which can be called a stubborn disease in plant diseases. There has been a trend of gradual aggravation in recent years, because it is quite different from the general diseases in terms of symptom characteristics, occurrence regularity and control measures, in order to facilitate correct identification, prevention and treatment, some key points of diagnosis, identification and prevention according to practice and access to relevant data are described in detail as follows:

1. Diagnosis and recognition. Symptom diagnosis can be divided into the following types: (1) discoloration: including "mosaic", "mottled" and "broken color". "mosaic" refers to the appearance of dark and green patches on diseased leaves. "mottled" means that there are chlorotic spots on the diseased leaves, the spots are larger, the edges are not obvious, and the distribution is uneven. (2) chlorosis and yellowing: the whole plant or some organs are light green or yellow. (3) spots and stripes: they often occur in leaves, stems, and other parts, showing necrotic spots, necrotic stripes, chlorotic spots or chlorotic stripes. (4) Ring spot and oak leaf: both often appear on the leaf, and the concentric spot is called "ring spot". Those with leaf-like discoloration patterns along the veins are called "oak leaves". (5) bright vein, yellow vein, vein band: bright vein and yellow vein are the early stages of mosaic symptoms, first, the transparent vein is called "bright vein", then the yellow vein is called "yellow vein", and the "vein band" turns dark green along the leaf vein. (6) wrinkled or rolled leaves: the deformation of local tissues or organs. The growth of leaf vein is inhibited, the mesophyll still grows, the leaf wrinkles and the leaf margin curls up or down. (7) ear process: protuberance occurs on the vein on the back of the diseased leaf, which is shaped like an ear, which is called "ear process".

2. Observation and analysis in peacetime is of great significance to the diagnosis of diseases. Virus diseases are easy to be confused with non-infectious diseases, especially those caused by element deficiency and air pollution. If there are healthy strains near the infected strains, they should be isolated immediately. The plant often can not recover after the disease. Most of the non-infectious diseases occur in pieces, and the disease can be restored to health by increasing nutrition and improving environmental conditions. Most of the symptoms of bluegrass virus disease are mosaic, yellowing, and often show systematic infection, less rot and wilting symptoms. Of course, virus symptoms are sometimes easy to change, different viruses in different host types and varieties, some virus diseases will appear hidden disease due to temperature and other changes. 3. The use of inclusions to diagnose plant cells infected by viruses will produce tiny individuals that are different from other cell structures. These individuals have different shapes and components, which are called "inclusions". Viral diseases can be diagnosed by microscopic observation of inclusions with special shapes, but the diagnosis with inclusions alone is not reliable.

Second, the mode of infection: 1. Sap infection usually occurs only in mosaic virus disease. In the process of planting, some viral diseases can be transmitted through friction between branches and leaves of diseased plants and healthy plants or human contact friction. Other management operations, such as dividing seedlings, trimming, cutting asexual reproduction materials, etc., make fingers or tools infected with diseased juice and spread the virus. two。 The main vectors were insects, especially aphids and leafhoppers, followed by soil nematodes and fungi. 3. The infection of asexual reproduction materials is due to the whole plant infection of the virus disease, once infected with the virus, the host plants and various parts generally carry the virus. Such as tubers, bulbs, bulbs, root tubers, walking stems, and so on, can spread viral diseases. 4. Plant material transmission is actually a contact infection between plant organisms and host plants, which can be divided into two types: one is the transmission of nematodes and fungi in soil, and the other is the transmission of virus-carrying organic matter in soil. So it's very easy to spread the virus.

Third, prevention and control methods: although effective radical measures have not been found, we can explore and master the law of the disease from production practice, and take a whole set of comprehensive preventive measures to control it. 1. First of all, the inspection of orchid strain with virus disease should be strengthened at the time of introduction, and non-toxic planting materials should be strictly used. The prevention and control of virus transmission vector uses various methods to eliminate aphids, leafhoppers and nematodes, cut off the route of transmission and prevent the occurrence of virus diseases. 3. In the process of cultivation, strive for intensive cultivation, adjust water and fertilizer, light, temperature and humidity, ventilation, light transmission and other links, there are no loopholes, create a good growth environment, so that the plant growth is robust, the virus can not take advantage of the deficiency. 4. always disinfect environmental hygiene and tools to avoid spreading the virus through fingers and tools as far as possible. 5. If it is found that the suspected virus disease of the orchid plant is first isolated and then controlled, if it is not effectively controlled, it should be pulled out and burned to avoid spreading and infecting other plants. no, no, no. 6. In recent years, with the progress of science and technology, many effective agents for viruses have been developed, such as phytolin, Shiduqing, Virobike, Virolimus, virion, virogram and so on. Author: Xu Maojin