Detailed Explanation of Leaf Spot Disease in Cymbidium and Its Related Genera

① Harm: Some orchids in Cymbidium and its related generaorchidsare often attacked by a fungus of the genus Cercospora, and this fungus is different from those that infect other plants. Its hosts include many species and hybrids in Cymbidium and the genus Grammatophyllum. ② Symptoms: The disease is characterized by tiny lesions on the underside of the leaves. The lesions are round, slightly sunken, dark brown, generally less than 1 mm in diameter, and often two or more lesions coalesce. The corresponding area on the center of the leaf blade is initially yellow-green, later turning brown with a pale yellow halo. Older leaves are more severely affected. ③ Control methods: Prepare a 1000-fold solution using benomyl 50% wettable powder, add a small amount of wetting agent, and spray 3 times at 2-week intervals. If necessary, spray once a month thereafter. If ferbam is used, dilute at a ratio of 800-fold and add an appropriate amount of spreader-sticker. This product is a protectant fungicide that protects plants. If the disease has already become a problem, susceptible varieties should be sprayed once every 2 weeks. Liu Zhongjian