Phytophthora cactorum a serious problem on prefinished Cattleya orchid liners from Thailand

The major pathogen on Cattleya orchids in Florida and in the New and Old World countries is Phytophthora cactorum (Lebert & Cohn) J. Schroet., which causes Black Rot during the wet months of the year. All species of Cattleya and their interspecific and intergeneric hybrids are susceptible. Phytophthora cactorum infects leaves, pseudobulbs, rhizomes, and flower buds. Shipments of prefinished Cattleya orchid liners from Thailand during the monsoon season often infected with P. cactorum. Orchid plants with visual symptoms of P. cactorum were removed from the shipment and drenched with fungicides such as Banrot, Natriphene, Shield Brite, Truban, and Phyton 27, Heritage, Shield Brite, Stature, Truban, Pentathlon, Aliette, Subdue Maxx, and Insignia, in an effort to salvage some of the plants. In spite of the effort to save the orchids, the level of Phytophthora over rode the attempt to control the fungus resulting in destroying the shipments. Cattleya liner shipments during the dry season are found to be P. cactorum free.