Symptoms and Control Methods of Odontoglossum Ringspot Disease

Distribution: Worldwide. Pathogen: Odontoglossum ringspot virus (ORSV) [Tobacco mosaicorchidvirus strain (TMV-O)]. Hosts: Arundina, Calanthe, Cattleya (Cattlop), Cymbidium, Dendrobium, Odontoglossum, Phaius (Phauys), Oncidium, Phalaenopsis, Vanda, Vanilla, etc. Symptoms: Infection of leaves. Necrotic tissue of the leaf forms concentric rings, or is interspersed with green areas. The rings may unite into various shapes. In the early stage of infection the symptoms are obvious and may cause leaf drop, but later they gradually become inconspicuous, though the plant still carries the virus. Control: Controlling viral diseases mainly involves removing diseased plants, improving environmental sanitation, and disinfecting tools, in order to prevent their spread. At present, the disinfectant solutions internationally recognized as better are: 1. 2% formalin and % sodium hydroxide aqueous solution (cannot be used again after it turns green); 2. 164 g of anhydrous or 377 g of crystalline trisodium phosphate (Na3PO4) added to 1 L (1000 cc) of water. They can be used to disinfect tools, the environment, etc. Note: This disease is widely distributed and includes many strains; the affectedorchidsymptoms also differ. In Cymbidium orchids it may appear as faint mosaic disease (Faintmosaic), chlorotic streak disease (Chlorotic streak) or diamond mottle disease (Diamondmottle); in Cattleya it harms the flowers, causing flower break disease (Flower break). Chen Xinqi, Ji Zhanhe