Pathogenic Constraints of Indian Orchid Growers: A Review

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Fungal and fungal-like pathogens (moulds) cause several diseases in orchids with common symptoms such as leaf spots, rusts, blights, rots, and wilts (Maketon et al., 2015;Sowanpreecha and Rerngsamran, 2018).The genus of these pathogens include soil borne root pathogens like Fusarium, Phytopthora, Sclerotinia, and Sclerotium as well as air-borne foliar pathogens like Alternaria, Botrytis, Colletotrichum, and Uredo which are found to be associated from vegetative to reproductive stage of the crop thereby pulling down the quantity and quality of the produce. Phytopthora sp.Phytopthora sp., a fungi-like oomycetous causes black rot disease in many orchid species.The species of Phytopthora associated with orchids are P. nicotianae, P. palmivora, and P. parasitica.The disease appears as water soaked small brown patches on the aerial plant parts.Black necrotic lesions develop on pseudobulbs and roots which spread upwards and cause complete defoliation of plant and complete degeneration of roots (Cating et al., 2010).Black lesions are also found in spikes, buds, and blossoms.New shoots also show the black rot symptoms which start from junction attached with the mother plants/pseudobulb.Disease occurrence at young stage of the crop results in damping off of seedlings.Infected bulbs act as major reservoir of pathogen.The sporangial mass of Phytopthora on the hyphae appears loose, white, cottony, and shines with tiny water droplets (Uchida and Aragaki, 1991).Black rot is reported in India on number of orchid species and hybrids of Ascocenda, Cattleya, Coelogyne, Cymbidium,