The Harm and Prevention and Control Methods of Orchid Virus Diseases

Viruses are relatively primitive organisms. They have no cellular structure and can only replicate by parasitizing host cells. Once infected, there is generally no specific drug for treatment, so viral diseases can only be prevented. Prevention can be achieved by improving environmental sanitation and raising cultivation techniques. More than 20 kinds of viruses that can infect orchids have been discovered so far. The more common ones include Cymbidium mosaic virus (CyMV), Cucumber mosaic virus (CMV), Dendrobium mosaic virus (DeMV), Cymbidium ringspot virus (CyRV), and others. Methods for preventing and controlling viral diseases: when viral diseases occur, promptly remove and burn diseased plants, and disinfect tools with a solution. Currently, the disinfectant solutions with relatively good effects include: 2% formalin and 2% sodium hydroxide aqueous solution, or a solution of 164 grams of anhydrous or 377 grams of crystalline trisodium phosphate plus 1 liter of water. Common viral diseases of orchids include:

1. Orchid mosaic disease

Also called orchid necrotic mosaic disease, black streak necrosis disease, etc. It is a common viral disease of orchids, and its hosts are extremely wide-ranging, including Cymbidium, Calanthe, Dendrobium, Paphiopedilum, Vanda, and others. The symptoms of affected plants are brown streaks between the leaf veins, which later become striped mosaic. Mosaic symptoms are obvious on new leaves, while on mature leaves the mosaic coloration is faint. About 3 weeks after viral infection, irregular chlorotic spots appear on new shoots, and as the leaves grow they become increasingly obvious, further developing into brown or grayish-brown necrotic spots. The pathogen of this disease is a viral disease caused by single or co-infection with Cucumber mosaic virus (CMV), Cymbidium mosaic virus (CyMV), and Dendrobium mosaic virus (DeMV). It is mostly seen in orchid plants cultivated in greenhouses and is transmitted by sap, so blades such as scissors and fingers used in cultivation management easily spread the virus, and water flowing from the bottom of infected pots can also transmit it.

Prevention and control methods:

When viral diseases occur, promptly remove and burn diseased plants, and disinfect tools with 2% formalin and 2% sodium hydroxide aqueous solution, or a solution of 164 grams of anhydrous or 377 grams of crystalline trisodium phosphate plus 1 liter of water.

2. Orchid necrotic spot disease

Also called orchid necrotic small spot disease, it is caused by infection with Orchid fleck virus and can infect Dendrobium, Cymbidium, Oncidium, and others. It generally occurs on leaves. On affected individuals, inconspicuous markings first appear on the leaf surface, then the leaf mesophyll cells collapse, and small yellowish-brown spots with sunken surfaces appear. In severe cases, reddish dark brown lesions appear. The markings are irregular and elongated, mixed with ring spots.

Prevention and control methods: usually pay attention to improving environmental sanitation conditions. When dividing plants, both fingers and tools should be washed with soapy water, and pots and growing media should be disinfected in advance. The disinfectant solution can use 2% formalin and 2% sodium hydroxide aqueous solution, or a solution of 164 grams of anhydrous or 377 grams of crystalline trisodium phosphate plus 1 liter of water. In addition, after diseased plants are found, they should be immediately removed and destroyed to control the spread of the disease.

3. Orchid ringspot disease

Also called orchid necrotic ringspot disease, it is one of the most common viral diseases of orchids. Its pathogen is Cymbidium ringspot virus (CyRV). Hosts include Cattleya, Cymbidium, and others. On the leaves of affected individuals, necrotic chlorotic ringspots or necrotic spots appear, and the plants become weak and stunted.

Prevention and control methods:

(1) Strengthen daily management. When propagating by division or changing pots and adding soil, minimize damage to leaves to prevent transmission through leaf sap friction.

(2) Fertilize reasonably, which can promote robust growth of orchid plants and also reduce disease.

(3) Diseased individuals should be promptly removed, and infected individuals must not be used as mother plants for propagation. In diseased areas, efforts should also be made to produce virus-free orchid seedlings through tissue culture.

(4) For diseased individuals, insecticides such as 40% dimethoate 1000-fold solution, or 50% malathion 800-fold solution, or 75% phoxim 1000-fold solution can also be sprayed to kill aphids, with good results.