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What is anthracnose in Chinese orchids? Let us learn about this disease

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Anthracnose in Chinese orchids affects orchids of the genus Cymbidium such as Spring Orchid (Cymbidium goeringii), Faber's Cymbidium (Cymbidium faberi), Four-season Orchid (Cymbidium ensifolium), Chinese Cymbidium (Cymbidium sinense), and Cold Orchid (Cymbidium kanran), causing scorched black spots on leaves and fruits, and in severe cases the entire leaf dies. Symptoms: In the early stage of the disease, round or oval red-brown spots appear in the middle of the leaf, and semicircular ones at the leaf margin. When they occur at the leaf base, large spots or a large number of them can also cause the entire leaf to die. In the later stage, the center of the spot becomes lighter in color, and the upper ring splits longitudinally. Spots on fruits are irregular, appearing as elongated dark brown patches. Pathogen: The disease is caused by several species of fungi. According to isolation and culture by the Shanghai Institute of Landscape Science,

Anthracnose in Chinese orchids affects orchids of the genus Cymbidium such as Spring Orchid (Cymbidium goeringii), Faber's Cymbidium (Cymbidium faberi), Four-season Orchid (Cymbidium ensifolium), Chinese Cymbidium (Cymbidium sinense), and Cold Orchid (Cymbidium kanran), causing scorched black spots on leaves and fruits, and in severe cases the entire leaf dies.

Symptoms: In the early stage of the disease, round or oval red-brown spots appear in the middle of the leaf, and semicircular ones at the leaf margin. When they occur at the leaf base, large spots or a large number of them can also cause the entire leaf to die. In the later stage, the center of the spot becomes lighter in color, and the upper ring splits longitudinally. Spots on fruits are irregular, appearing as elongated dark brown patches.

Pathogen: The disease is caused by several species of fungi. According to isolation and culture by the Shanghai Institute of Landscape Science, the two species that frequently appear are Colletotrichum orchidearum Allesch and C. orchidearum f. cymbidium Allesch. The anthracnose pathogen occurring on Cold Orchid and Faber's Cymbidium may be C. orchidearum f. cymbidium; the anthracnose pathogen occurring on Sichuan Spring Orchid, Four-season Orchid, Po Orchid, and Chinese Cymbidium is mostly Colletotrichum orchidearum.

According to reports from Beijing, the pathogen of orchid anthracnose also includes fungi of the genus Gloeosporium. The acervulus of Colletotrichum orchidearum is round, small and black, and grows on both sides of the leaf. The setae are dark brown, with 3-4 septa, straight or slightly curved, tapering at the tip, measuring 50-100*3-5 microns. The conidia are cylindrical, measuring 12-20*4-6 microns, slightly smaller at one end, transparent and colorless, single-celled, with oil droplets or granular inclusions. The conidiophores are thick and short. The optimum growth temperature of the pathogen is 25°C. The optimum temperature for germination is 25-30°C.

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