What are the control measures for black spot disease in orchids?

Orchid black spot disease, also known as round spot disease, occurs in Fujian, Yunnan, Jiangsu, Shanghai, Nanjing and Guangdong. In 1983, a major outbreak of orchid black spot disease occurred in Guangzhou, with the incidence rate in some nurseries reaching 92.8% and the mortality rate 26.8%, causing great economic losses. The control measures are as follows:

　　

1. Strengthen quarantine, paying particular attention to quarantine at the place of origin. New soil free of pathogens should be selected for planting orchids; when old soil is used, it must be sterilized with formaldehyde solution. Select disease-free seedlings to control the spread of the disease. After planting, spray the soil surface with New High-Lipid Film, which can preserve soil moisture, prevent water evaporation, protect against sun and drought, prevent soil compaction, suffocate and isolate sources of pests and diseases, and protect seedlings so they grow vigorously.

　　

2. Maintain a growing environment with good ventilation and light transmission, and provide shade in summer and autumn. Water and fertilize reasonably, and spray New High-Lipid Film to preserve moisture and fertilizer. Promptly remove diseased leaves and fallen leaves, cut off the diseased spots in the middle of the leaves, and burn them in a centralized manner. After flowering begins, spray Huaduo Zhuangdiling at the appropriate time, which can promote strong flower buds, large petals, vivid flower colors, rich fragrance and a longer flowering period.

　　

3. Before the disease occurs, spray an appropriate amount of Bordeaux mixture plus New High-Lipid Film 2 times, once every 10-15 days. During the disease period, use targeted agents plus New High-Lipid Film for control. When spraying, make sure to spray evenly on both the front and back sides of the leaves. Spray once every 7-10 days, for several consecutive applications, and alternating fungicides will give better results.