Experience Sharing on the Prevention and Control of Orchid Black Spot Disease

A visitor entering the small orchid nursery asked: Master, how is it that yourorchidsgrow so tenderly green, with such smooth leaf surfaces and no black spots? Indeed, this must be explained from the beginning. These black spots are an orchid disease called anthracnose, also known as black spot disease. It mainly attacks orchid leaves, with oval-shaped lesions appearing on the leaf surface, growing from small to large, turning from yellow to black, and in severe cases merging into patches of rot. The disease occurs more frequently every year during the plum rain season, and mostly damages new leaves (shoots). Many householdorchid growers, and even many small orchid nurseries, have this black spot disease, which greatly affects theorchids'growth and flowering, and also reduces theorchids'ornamental value. How does the author prevent and control it? 1. Choose a good orchid site: Select and create a place with good air circulation and fresh, pollution-free air as the orchid site. Around the orchids, it is best to have green trees, water lakes, and several small water jars to help increase air humidity. Use bamboo blinds for the shade structure, with shade nets placed on top; the shading level should preferably be automatically adjustable, opened in the morning and evening for ventilation. The spacing of orchid pots should be appropriate to allow air circulation. 2. Keep the orchid site clean and hygienic: Frequently clean up diseased leaves and dead branches of orchids, sweep the floor.Orchid plantsWhen dividing pots or purchasing new orchid seedlings, use thiophanate-methyl to disinfect and kill bacteria, dry them before planting. The growing medium (humus soil, pond mud, charcoal...) must be sterilized at high temperature or sun-dried before use, so that bacteria cannot enter the orchid pots (site). 3. Cultivate robust orchid seedlings and enhance disease resistance: Fertilizing and pest control must be carried out according to plan. During the orchid's dormant season, use a mixture of thiophanate-methyl, carbendazim, and buprofezin sprayed on the leaf surface more than three times, which both removes pests and eliminates bacteria. This enables new seedlings to grow vigorously in early spring. Afterward, spray thiophanate-methyl and carbendazim once every 20 days. Combined with proper fertilization,orchid plantsbecome robust with strong disease resistance, and black spot disease is unlikely to occur." 4. Master seasonal prevention and control: Black spot disease is most likely to occur every year during the plum rain season, especially when long periods of rain give way to clear weather; spray medicine promptly for prevention and control. During the sprouting stages oforchid plantsin spring and autumn, new seedlings have poor disease resistance, so strengthen chemical prevention and control to ensure normal growth of orchid seedlings. 5. Frequently observe orchid plants to prevent orchid disease: Regularly observe the growth conditions of orchid plants and seedlings. Once black spot disease is discovered, promptly prune and remove affected parts, destroy them in a centralized manner, clean up the surrounding environment, strengthen ventilation, reduce moisture, and immediately apply carbendazim and thiophanate-methyl at 600-800 times dilution for spraying, once every 15 days, for three consecutive times, which can inhibit the development of black spot disease. The author is an ordinaryorchid-growingenthusiast. The small orchid nursery with more than 150 pots oforchidsthat I cultivate, although growing quite well, still has many shortcomings. The prevention and control methods for the disease spots mentioned above may not be fully proven, and are only for the reference of fellow orchid enthusiasts. (Lin Jinxiang)