Simple Management of Chinese Orchids, Part 4: Teach You to Easily Grow Orchids Well

Common diseases of Chinese orchids include blight, anthracnose, sclerotinia rot, root rot, wilt disease,soft rotdisease, Bras disease, rust, and so on. In this region, anthracnose is the most widespread threat to Chinese orchids; wilt disease (caused by Fusarium) has also shown a rapid spread in recent years. Anthracnose is commonly known as black spot disease or black leaf spot disease. It can occur in spring, summer, and autumn (and also in winter), but is most severe in summer and autumn. When the disease strikes, black spots mostly first appear on the upper part of young leaves, and in severe cases the upper and lower leaf surfaces can be covered with black spots of varying sizes. Anthracnose can flare up malignantly: at this stage the black spots appear black with yellow edges, and around these as centers, many more black-with-yellow spots can appear, forming a circular disease ring. Under harsh sunlight, anthracnose is prone to occur, and orchid plants with a thin cuticle (commonly called powdery) are also prone to developing black spots. Rainwater and waterfrom wateringsplashing and running off have already spread the infection. I remember years ago when I first came to Chencun to establish Feng's Orchid Garden, because I purchased a large number of wild orchids at one time, anthracnose and blight (with water-soaked patches on the leaves) broke out simultaneously. At that time I used six chemicals in rotation, including thiophanate-methyl, chlorothalonil, and Topsin, and it took two months to cure the disease. For this disease, I now mainly spray 500 times diluted Topsin on the leaf surfaces, once every half month in summer and autumn, with good results. While spraying, I also remove severely diseased leaves and acutely affected leaves to reduce the source of infection. Wilt disease has spread rapidly in this region in recent years, occurring mainly in the Baimo strain of Suxin orchids; other cultivated orchids and new varieties,wild-collected orchidshave also gradually become infected and fallen ill. In ordinary orchid gardens, losing dozens of pots a year to this disease is already commonplace, and in severe cases more than half die. Once the disease begins, the affected leaves rapidly turn yellow and drop, and it is difficult to save them. According to research, the pathogen is Fusarium, which spreads through water and enters through stomata and wounds. Some people believe it is related to the acidity of the growing medium, and therefore use potassium permanganate, alkaline grass solutions, and wood ash water for control, but the results are poor. However, Chinese orchids prefer slightly acidic growing media. Therefore, once this disease is discovered, there is no way to save the plant, so only prevention is possible. But if alkaline liquids were applied across the board, it would inevitably greatly reduce the acidity of the growing medium, which is unfavorable to the growth of Chinese orchids, so this is impractical. Discarding and destroying diseased plants, replacing the growing medium, and disinfecting orchid plant wounds and scissors are preventive measures. In terms of medication, soaking healthy plants for several hours in a 2000 times dilution of 25% prochloraz emulsifiable concentrate, and applying a mixture of 2000 times dilution of 25% prochloraz emulsifiable concentrate and 40% procymidone powder once every 5-7 days for three consecutive times, is said to also have a preventive and curative effect. In addition, one can use "Hemiao brand - RC Revitalizer": spray on leaves at 1200-1500 times dilution, or dilute with water at 3000-5000 times to water the roots, both having good results. Regarding this disease, I believe the orchid community should attach great importance to it and quickly research an effective set of prevention and control methods. Excerpted from "OrchidTreasure Book" Macao, China Feng Gangyi