The Complete Guide to Anthracnose Prevention and Control in the Medicinal Plant Orchid (Cymbidium)

OrchidGrowing: Medicinal PlantsOrchid(Orchid) Anthracnose

The scientific name of the orchid is Cymbidium spp., a perennial herbaceous plant of the family Orchidaceae. It includesCymbidium ensifolium, Cymbidium floribundum, and Cymbidium faberi, three species. The roots, leaves, flowers, and fruits of the orchid can all be used as medicine. It has the effects of nourishing yin and clearing the lungs, and resolving phlegm and relieving cough. Zhejiang, Shanghai, Jiangsu, Anhui, Jiangxi, Hubei, Hunan, Sichuan, Guizhou, Yunnan, Guangdong, and Fujian all havecultivation。

Anthracnose

Symptoms mainly affect the leaves and fruits. Leaf infection often occurs at the leaf tip or leaf margin, initially producing small round to oval dark brown spots, which then gradually expand; the center of the lesion becomes light brown or grayish white, while the edge is dark brown to blackish brown, with a distinct boundary between diseased and healthy tissue. Lesion expansion is limited by the leaf veins; lesions on the leaf tip are triangular, while those on the leaf margin are semicircular. Fruit infection produces spindle-shaped dark brown lesions, and later small black dots may appear on the diseased area, namely the pathogen's acervuli.

The pathogen Glomerella cingulata (Stonem.) Spauld. et Schrenk is called Glomerella cingulata, a fungus of the subphylum Ascomycotina. Its asexual state is Colletotrichum gloeosporioides Penz., called Colletotrichum gloeosporioides, a fungus of the subphylum Deuteromycotina. For morphological characteristics, see anthracnose of goji berry.

Transmission routes and disease conditions The pathogen mainly overwinters as mycelium in diseased leaf tissue; in the south it can also overwinter as conidia. In April of the following year, the mycelium in the diseased area resumes activity and expands to adjacent areas, producing new reddish-brown lesions. The conidia produced on the lesions are spread by wind and rain. When there is a water film or water droplets on the leaf surface, the conidia germinate and invade through wounds, and after a 2-3 week incubation period, the disease develops. A temperature of 20-29°C and relative humidity above 80% are suitable for the expansion of this disease. In the Shanghai area, old leaves begin to develop the disease in early April, and the disease spreads relatively quickly during the plum rain season, gradually stopping after July; new leaves mostly begin to develop the disease from August, and the disease is severe under rainy conditions or when planting is too dense.

Control methods (1) Strengthen cultivation management. Use shade nets for shading in orchid nurseries or greenhouses, maintain ventilation and light penetration, thoroughly prune diseased leaves from plants in winter, clear fallen leaves from the ground, and burn them in a centralized manner. (2) At the early stage of the disease, spray 25% carbendazim wettable powder at 500 times dilution, or 36% thiophanate-methyl suspension concentrate at 600 times dilution, or 25% benomyl emulsifiable concentrate at 800 times dilution. Apply once every 10 days or so, for 2-3 consecutive treatments.