How to prevent orchid diseases? A summary of my experience

(1) Disease symptoms: (1) Irregular brown spots appear on the leaf surface, and the affected area keeps expanding, or swirl-shaped brown patterns appear. This is called anthracnose. (2) Small brown spots appear on the leaf surface, then gradually expand, with the color changing from yellow to brown, and then to dark brown; the diseased spots have a yellow halo around them and are slightly sunken in the middle. This is called iron artillery disease. (3) The epidermis on the underside of the leaf bulges into rust-brown, sesame-sized raised objects. This is called rust disease. (4) When young shoots are growing, the area near the leaf sheath (commonly called the sheath) appears brown and water-soaked, and soon rot develops, with a foul odor. This is calledsoft rotdisease (commonly called basal shoot rot). (5) The base of the pseudobulb (orchid head) turns black and rots, and white cotton-like mycelium is produced at the diseased spots, after which small granular sclerotia form; the sclerotia are initially white and turn brown after hardening. This is called southern blight. (6) The roots have brown spots, which then form ring-shaped or band-shaped brown sunken areas and rot, until finally only skin and bones remain. After the roots rot, their function of absorbing water and nutrients is lost, and the leaf surface and pseudobulbs gradually shrivel and twist. This is called root rot. (7) Irregular gray-white patches appear on the leaf surface, chlorophyll disappears, there is obvious sunkenness, and shriveling occurs. This is the viral disease thatorchid growersfear upon seeing it (transliterated in Taiwan as "Bailas"). In addition, there are brown spot disease; bacterial wilt; and so on. (2) Disease prevention: The various diseases listed are all related in their causes to the following factors: (1)Orchid growinglocation: To groworchidswell, one must first knowthe orchids'growth habits.Orchid growingpioneer Ou Jince discussed this in detail in "Linghai Lanyan." Too much sunlight without timely watering, or excessive shading and poor ventilation, are the root causes of orchid diseases. (2) Orchid growing medium: The success or failure of orchid growing depends entirely on whether the growing medium is suitable. Orchid roots are semi-epiphytic roots, so the growing medium must be loose and breathable for the root system to grow vigorously; conversely, if the medium is compacted and air cannot circulate, how can roots grow? Even if the orchids do not get sick, they will certainly produce weak shoots, and the offspring will be weak and unable to resist disease. Once pathogens invade, they will be infected first. (3) Fertilization and maintenance: Orchids originally grow in secluded valleys. Their native land is mostly slightly fertile areas, and there is also an appropriate amount of humidity, not overly dry, so they can grow smoothly. Orchid lovers move them to set locations to propagate them, hoping thatthe orchidswill grow luxuriantly. Fearing that nutrients are insufficient, they fertilize continuously, and at high concentration. Little do they know that this action produces the opposite effect. If orchids are overfertilized, they not only cannot grow normally, but instead suffer fertilizer damage. (4) Pesticide spraying: Although pesticides have a certain effect on disease prevention and control, excessive use will reduce the orchid's own disease resistance; spraying pesticides at too high a concentration can also cause phytotoxicity. One must be cautious. In summary, for orchid disease prevention, what is important is still to pay attention to the suitability of the orchid growing location and the selection of the growing medium, proper fertilization and nutrition, and appropriate pesticide spraying. If this can be followed, then the orchids will certainly be robust, and diseases will naturally decrease. Huang Guozhu