Symptom Identification and Control Methods of Cymbidium Mosaic Virus

1. Damage: In various parts of the worldorchidproduction areas, Cymbidiumorchidmosaic virus has mostly been found. It is especially common in the United States and Japan. In China, it occurs commonly in Shanghai, Xiamen, Fuzhou, Guangzhou, Chengdu, Shenzhen and other places. When Cymbidiumorchidmosaic virus infects alone, its impact on orchid growth is not great, but when it co-infects with other viruses, it can cause necrosis, poor plant growth and other symptoms. The disease can harm many orchid plants such as Cattleya,Cymbidium, Dendrobium, Vanilla, Phaius, Vanda, Paphiopedilum and more than 2O orchid genera, causing mosaic or necrotic spots. When inoculated onto plants such as Cassia occidentalis, Senna tora, Datura, Chenopodium amaranticolor and Tetragonia, it causes local necrotic spots or chlorotic spots. 2. Symptoms: On new orchid leaves it causes mosaic or necrosis, or produces chlorotic streak spots along the veins. On inoculated leaves of Cattleya it forms local necrosis. If it co-infects with ORSV, it can cause brown necrosis on flower buds and cause mosaic in Dendrobium. 3. Pathogen:Cymbidiummosaic virus (CyMV) particles are filamentous, 475nmX12nm, with a nucleic acid RNA content of 6%, a helical nucleocapsid, a sedimentation coefficient of 144S, a thermal inactivation point of 65-70°C, a dilution end point of 5X10*10*10*10*10, and a longevity in vitro at room temperature of 7-3O days. 4. Disease occurrence pattern: Transmitted by sap, and the green peach aphid can transmit the virus. The virus persists for a relatively long time in the sap of diseased leaves; in some orchid varieties it takes 2 months to lose its infectivity. Some diseased orchid plants remain diseased for life, and the new shoots they sprout also all carry the virus. If healthy disease-free seedlings are planted in clay pots or soil that have previously been used to grow virus-carryingorchids, the plants are prone to developing the disease. 5. Control methods: (1) For some precious virus-free orchids, they must be cultivated in isolation from orchid production basescultivation; (2) For horticultural operations such as division and repotting, fingers and tools must be disinfected again after planting each plant; (3) Roots cannot be washed in the same container; running water should be used to wash the roots; (4) The media used for cultivatingorchidssuch as peat, moss and gravel should be disinfected. (Liu Zhongjian)