Identification and Control Methods for Common Diseases of Orchids

Currentlycultivatedorchids are almost all original species, which should originally possess strong innate disease resistance. However, because they have long been grown by people in pots, their wild characteristics have long since been lost entirely due to differences in environment or improper management. After a pathogen enters the plant, orchids do not immediately show obvious symptoms, so for a layperson, before the orchid shows any abnormality, it is very difficult to notice that the beloved orchid has already become sick. In addition, because symptoms caused by the same pathogen can differ in color and form depending on time and place, it is truly not easy for a layperson to judge whether the plant is sick. Since once an orchid has been sick, endless problems will follow afterward, so in normal times one must pay close attention and not give pathogens a chance to invade the orchid plant. When purchasing orchids, first carefully inspect the roots to see whether they suffer from some kind of disease. Tools that have come into contact with orchids should be thoroughly disinfected, and old growing material should be destroyed and discarded, so as to cut off the chance of pathogens entering from the roots. The following lists the parts most commonly damaged and the types of diseases for explanation. Diseases of young shoots During the young shoot growth period from April to September, if the leaf sheath is healthy and the root of the new shoot suddenly turns tea-brown and rots, this is because it has contractedsoft rotdisease. The preventive method is: do not let water remain on the young shoots. If the young shoot stops growing while still tender and black spots appear, this is caused by anthracnose. The preventive method is to spray an organic sulfur fungicide (Dacotech) once or twice a month. Diseases of leaves, roots, and petals Anthracnose: After the temperature rises, irregular brown spots appear on the leaves and gradually expand in area, or swirl-shaped brown patterns appear, which indicates that anthracnose has been contracted. The preventive method is the same as above. Leaf blight: The leaf tip suddenly turns brown and dries up, or the base of the leaf or the leaf sheath changes color and black spots appear around it, indicating leaf blight. When the roots are all impaired, it is very easy to contract this disease. The preventive method is the same as above. Atrophy disease: When part of the leaf shows white spots, or yellow stripes, or necrotic lesions, it indicates atrophy disease. This disease cannot be prevented with chemicals. Once this disease is seen, it must be isolated immediately. Because this disease is easily transmitted through water, the watering method of placing the pot in a bucket to soak, or the management method of placing it under a shelf, must be immediately suspended to prevent this disease from being transmitted to other plants. soft rotdisease: At high temperatures, the leaf base suddenly turns yellow-brown, and the pseudobulb also rots, indicating thatsoft rotdisease has been contracted. The preventive method is to keep ventilation and drainage in good condition, and do not let water remain on the new shoots. Southern blight: At high temperatures, white fine threads appear near the leaf base or on the pseudobulb, and many brown granules are produced. This is a disease called southern blight. In the blink of an eye it can cause the entire orchid to wither and die, and it also causes white mycelium to appear around the roots. Because there is no chemical treatment for it, once such a diseased plant appears, it should immediately be destroyed and discarded, or new growing material should be used to plant and isolate it. The preventive method is to keep the pot as clean as possible, and do not let the pot come into direct contact with the ground. Gray mold: When flowering, the petals show water-soaked, discolored conditions, and mold also grows, which indicates gray mold. The preventive method is not to let the petals get wet, and when the flower buds are still very small, spray them with a 2000-fold dilution of Benlate, and do not let a high-temperature, high-humidity state occur indoors. (Zhang Fengrong)