Detailed Explanation of Leaf Spot Disease Caused by Septoria Fungi

Orchids affected by this diseaseorchidsinclude: Cattleya, Dendrobium, Laelia, Odontoglossum, Oncidium, and Cymbidiumorchids, etc. On Dendrobium, the symptoms first appear as tiny, sunken yellow lesions on both sides of the leaves; the spots quickly develop into circular to oval or irregular shapes, dark brown to black, and some may merge into irregular patches. If the disease is severe, or if it occurs at the base of the leaves, the leaves may drop. On older lesions and fallen diseased leaves, fungal conidia or fruiting body structures are produced, becoming the source of infection for subsequently susceptible plants. The pathogen of this disease is: Septoria selenophomoides. Spray with benomyl 50% wettable powder diluted 1000 times with a little wetting agent added, once every two weeks for a total of 3 times; thereafter, if necessary, apply once a month. Ferbam and chlorothalonil 2787 can also be used to protect plants against pathogen infection, at a dilution of 800 times. For Dendrobiumorchids, the above two types of fungicides should be used 1 month before natural leaf drop, and all fallen leaves showing symptoms should be collected and destroyed. In other seasons, the above two types of fungicides are beneficial for both deciduous and evergreen Dendrobium. (Liu Zhongjian)