Symptom Identification and Control Methods for Bacterial Leaf Rot

Distribution: Asia and the United States. Pathogen: Erwinia chrysanthemi. Hosts: Dendrobium, Vanda, etc. Symptoms: Infected leaves of Dendrobium turn yellow and water-soaked; Vanda shows semi-transparent patches on the leaves. Eventually the lesions turn black and sunken. Control: This disease is mainly transmitted through wounds, such as breakage from bumping or insect bites, so these should be avoided as much as possible. Diseased leaves should be removed as soon as they are found, and the wounds should be coated with Bordeaux mixture. The whole plant can be soaked in a 0.1% potassium permanganate solution for 5 minutes, then rinsed and dried in the sun for 15 minutes before being planted in the shade. Spraying with 0.5% Bordeaux mixture or 200 mg/L agricultural streptomycin also has some effect. When the disease is severe or spreading rapidly, overhead watering is especially inadvisable. Excessively high humidity also easily triggers this disease. (Chen Xinqi, Ji Zhanhe)