Common Diseases of Orchids and Their Control Methods

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 control, so viral diseases can only be prevented by improving environmental hygiene and raising cultivation standards. More than 20 viruses capable of infecting orchids have been discovered so far. The more common ones include Cymbidium mosaic virus (CyMV), Cucumber mosaic virus (CMV), Dendrobium mosaic virus (DeMV), and Cymbidium ringspot virus (CyRV). Methods for controlling viral diseases: when a viral disease occurs, promptly remove and burn the diseased plants, and disinfect tools with a solution. Currently, the more effective disinfectant solutions include: 2% formalin and 2% sodium hydroxide aqueous solution, or a solution of 164 g of anhydrous or 377 g of crystalline trisodium phosphate plus 1 liter of water. Common viral diseases of orchids include:

1. Orchid mosaic disease

Also known as orchid necrotic mosaic disease, black stripe necrosis disease, etc., it is a common viral disease of orchids. Its hosts are extremely wide-ranging, including Cymbidium, Calanthe, Dendrobium, Paphiopedilum, Vanda, etc. The symptoms of damage are brown streaks between the veins, which later become striped mosaic. The mosaic symptoms are obvious on new leaves, while the mosaic color on mature leaves is faint. About 3 weeks after viral infection, irregular chlorotic spots appear on new shoots and become more and more obvious as the leaves grow, then develop 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 scissors and other blades and fingers used in cultivation management easily spread the virus, and water flowing from the bottom of infected pots can also transmit it.

Control methods:

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

2. Orchid necrotic spot disease

Also known as orchid necrotic small spot disease, it is caused by infection with Orchid small spot virus and can infect Dendrobium, Cymbidium, Oncidium, etc. It generally occurs on leaves. On the leaf surface of affected individuals, inconspicuous markings first appear, followed by collapse of leaf mesophyll cells, with sunken yellowish-brown small spots appearing. In severe cases, reddish dark brown lesions appear, and the markings may be irregular or elongated, while ring spots are also mixed in.

Control methods: usually pay attention to improving environmental hygiene 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 a 2% formalin and 2% sodium hydroxide aqueous solution, or a solution of 164 g of anhydrous or 377 g of crystalline trisodium phosphate plus 1 liter of water. In addition, after diseased plants are found, they must be immediately removed and destroyed to control the spread of the disease.