Symptoms of Sooty Mold on Orchids and Its Control Methods

This disease can affect Vanda, Dendrobium and Cattleya orchids. Because the pathogen only grows epiphytically on the leaf surface and does not penetrate the epidermis, the harm it causes toorchidsis not great either, but since it covers the leaf surface with a layer of soot-like material, it affects their ornamental value, and because the pathogen's covering of the leaf surface affects normal photosynthesis, it interferes with normal growth. Its symptoms are a layer of soot-like lesions covering both sides of the leaves and the pseudobulbs, with unclear margins, dark black or gray, variable in size, generally 2-5 cm in diameter. Individual spots tend to be circular, but may also be oval or irregular. Several lesions often merge together to form larger irregular patches. The pathogenic fungus of this disease has been identified as Gloeodes pomigena. Because this disease mostly occurs in shaded areas inside the orchid house, measures such as providing sufficient light, maintaining moderate warmth and promoting faster drying of the leaves all help to control the disease. Wipe the affected areas with a damp cloth strip to remove the epiphytic pathogen from the surface. (Liu Zhongjian)