Control measures of black spot in orchids

Orchid black spot, also known as round spot, occurs in Fujian, Yunnan, Jiangsu, Shanghai, Nanjing and Guangdong. Orchid black spot epidemic in Guangzhou in 1983, the incidence in some nurseries was as high as 92.8%, and the mortality rate was 26.8%, resulting in great economic losses. The prevention and control measures are as follows: 1. Strengthen quarantine, pay special attention to quarantine of producing area, choose new soil without bacteria to plant orchids, and disinfect soil with formaldehyde solution when using old soil. Disease-free seedlings were selected to control the spread of disease. After planting, spraying soil surface with new high-fat film can preserve soil moisture, prevent moisture evaporation, prevent sun and drought, prevent soil layer from hardening, suffocate and isolate the source of diseases and insect pests, and protect the growth of seedlings. 2. Keep the growth environment ventilated and transparent, and shade in summer and autumn. Reasonable watering and fertilization, and spraying new high-fat film to preserve soil moisture and fertilizer. Remove the diseased leaves and fallen leaves in time, cut off the disease spots in the upper and middle part of the leaves, and burn them centrally. Spraying Zhuangtiling at the right time after flowering can make the buds strong, the petals enlarged, the flowers colorful, the fragrance strong and the florescence prolonged. 3. Spray Bordeaux solution and new high lipid membrane twice before onset, once every 10 to 15 days. During the onset period, targeted agents and new high lipid membrane were used for prevention and treatment. When spraying, pay attention to spray evenly on both sides of the blade. The effect is better when fungicides are used alternately once every 10 days for many times.