Understanding Black Spot (Anthracnose) Problems

Analysis ---- Black Spot (Anthracnose) A while ago, an orchid-growing friend asked about the prevention and treatment of black spot, and yesterday a local orchid friend also brought up this matter, feeling very troubled by it. Seeing that my orchids were doing well, he asked how to prevent and treat it properly, seeking discussion. Looking at the orchids of friends both online and locally, in September they showed outbreaks of black spot disease to varying degrees. Based on my own cultivation experience, pay attention to the following points: One: The growing medium should be loose and breathable, and when potting, the orchid roots must not touch the pot wall. Two: During high-humidity seasons, try not to water or spray fertilizer or pesticide during the day. When watering, water thoroughly, create conditions to increase the day-night temperature difference, preferably no less than 8°C. Three: Foliar fertilizer must not be too concentrated. If growing for your own enjoyment, it is best to spray less. Spraying foliar fertilizer or water should also be done in the evening, to suit the physiological needs of the orchid. Four: At seasonal transitions, during periods of fluctuating hot and cold weather, especially in September, there are more stuffy and hot days as well as more cool days. This is also the time when orchid growers are most likely to be negligent, rushing to fertilize and repot, with the potting medium too wet. Once the temperature rises again, within one or two days the orchids suddenly break out with black spot. The causes are many-sided: poor root systems, excessive spraying of fertilizer, not paying attention to the timing of water control, the potting medium being too wet after the weather warms up again, poor nighttime ventilation, spraying medication at the wrong time, and so on. Five: When the weather suddenly turns cool in September, focus on disease prevention and promptly spray or water with fungicides such as thiophanate-methyl. Six: Orchid growers cultivating on balconies should pay attention to the day-night temperature difference. In September, increase the use of fans in the evening, which can also reduce the probability of disease. Seven: For those severely affected, it is recommended to repot, wash clean and cut off diseased and rotted roots, and dry them. At this time the weather should be cool, for about 12 hours. After potting, water with thiophanate-methyl as the settling water, and the next day water thoroughly again with clean water. This generally brings the disease under control. By following the above principles in my cultivation, the probability of this disease actually occurring is indeed relatively small. Growing orchids is about cultivating your state of mind. As long as you understand the physiological characteristics of orchids, some diseases can indeed be prevented. Wishing orchid friends a good mood in growing orchids and every success. There is plenty of information online about the pathology of this disease, so I will not elaborate further. The above is for the reference of orchid friends. http://www.shorchid.com/lhbbs/dispbbs.asp?boardID=8&ID=620&page=8