Full Guide to Identifying and Controlling Anthracnose

There are many species of anthracnose pathogens, and the symptoms they cause on orchid leaves are similar, sometimes difficult to distinguish, and some people also call it leaf spot disease. The optimum growth temperature for anthracnose pathogens is 22-28°C. During the spring and autumn rainy seasons or the plum rain season, and when orchid plants are at the budding or flowering stage, when the growth vigor of the orchid plant is relatively weak, they are most susceptible to the disease. Anthracnose pathogens mostly harm orchid leaves, and occasionally can also be found on pseudobulbs. When orchid plants suffer mechanical injuries such as sunburn, cold damage, external friction wounds, and root damage, causing the growth vigor of the orchid plant to weaken, they are most susceptible to anthracnose pathogens. Near the leaf tip or on the underside of the leaf, small black spots appear, gradually expanding into irregular lesions. Brown ring rot spots appear on the leaves, gradually expanding into large light brown lesions, slightly sunken in appearance. When anthracnose pathogen infection is severe, old leaves sometimes turn yellow and drop prematurely. Control methods: (1) Anthracnose pathogens have a very wide host range and are often spread by splashing water.cultivationmanagement, try not to keep the leaves wet for too long, and avoid supplying water by drenching the entire plant, so as to prevent the orchid plant from being harmed by anthracnose, which affects its photosynthetic capacity and restricts the growth of orchid roots. (2) Strengthen Chinese orchidcultivationmanagement, cultivate strong orchid plants, and avoid pathogen infection caused by artificial or mechanical abrasions. (3) Avoid weakening of the orchid plant's growth vigor caused by cold damage or sunburn, which reduces resistance to pathogens. (4) When excessive nitrogen fertilizer is applied, the orchid plant tissues are softer and pathogens are more likely to invade and cause harm. More organic plant growth promoters and low-nitrogen, high-phosphorus, high-potassium fertilizers should be applied to help resist disease. (5) Keep the leaves upright; when leaves droop, water droplets are more likely to accumulate at the leaf tip, the leaf tip is more susceptible to infection, and the leaf tip scorches (6) During seasons of high susceptibility, keep the leaves dry as much as possible. (7) Prevention is more important than treatment; use on a full schedule: (a) 70% chlorothalonil wettable powder at 1,000 times dilution; (b) 40% procymidone wettable powder at 2,000 times dilution; (c) 50% daconil wettable powder at 1,000 times dilution; Add spreading agent at 1,500 times dilution to enhance the pesticide. In summer, use once every 10-14 days; in winter, use once every 20-30 days, alternating them. When spraying, make sure the entire leaf surface is evenly wet; the finer the spray particles, the more effective the result. (8) When disease is found, cut off the diseased leaves, take them away and burn them, to avoid infecting other healthy leaves again. Immediately use 70% chlorothalonil wettable powder at 600 times dilution, once every seven days, and three consecutive applications can control the disease progression. Within two days after applying the pesticide, do not water by drenching, so as not to affect the fungicidal effect. The control of anthracnose is closely related to whether the Chinese orchidcultivationmanager's choice of pesticide type, timing of application, and application techniques are correct. In the occurrence of anthracnose, the initial symptoms mostly begin with infection on the underside of the leaf. When cultivation managers routinely apply pesticides for disease control, if the pressure of the spraying equipment used is insufficient and the spray fineness is insufficient, and if during spraying the leaf surface and leaf underside are not thoroughly and evenly sprayed, the pathogens cannot be completely eliminated. When the appropriate environment and sufficient nutrient sources are available, the pathogens will spread and expand again. After the lesions expand, the proper functions of the leaves are reduced, and quality and yield will be greatly reduced. Therefore, the control of anthracnose is a very important task. As long as cultivation managers use pesticides effective against anthracnose before the rainy season arrives and on a regular basis for control work. When spraying, use the finest mist spray method, spraying the orchid plants and the surrounding orchid room, especially the underside of the leaves, which is most important. And regularly clean the dirt on the floor of the orchid room, then the orchid plants grown by cultivation managers will not suffer losses due to anthracnose infection.