Identification and Control Methods of Bacterial Brown Spot

Distribution: Worldwide; more common in Asia and the United States. Pathogen: Pseudomonas cattleyae, Pseudomonas cypripedii, etc. Hosts: Very extensive, mainly including Ascocentrum, Aerides, Cattleya, Cymbidium, Cypripedium, Dendrobium, Gastrochilus, Paphiopedilum, Phalaenopsis, Vanda, etc. Symptoms: Soft, water-soaked small spots appear on the leaves, then develop into clearly defined, sunken, brown or black spots. In Phalaenopsis, these spots are blister-like and rapidly expand and coalesce, with a yellow or light green halo around the margin. The disease usually progresses rapidly and can cause the death of the entire plant. Control: Pay attention to ventilation and sanitation, and avoid watering over the top of the plant, because humid and warm environments are most likely to cause this disease. When diseased plants are found, the infected organs or the entire plant may be removed as appropriate, then sprayed with 0.5% Bordeaux mixture or 200 mg/L agricultural streptomycin, or soaked in 0.1% potassium permanganate solution for 5 minutes, washed clean, dried, and then replanted. (Chen Xinqi, Ji Zhanhe)