How to effectively prevent and control diseases before potting orchids

Before potting, do a good job of disinfecting the seedlings, soil, and pots; keep the potting medium loose and airy, do not let it become waterlogged, strengthen management, and fertilize reasonably to enhance disease resistance. When disease is discovered, immediately use medication for control. Pesticides such as Bordeaux mixture, myclobutanil, and chlorothalonil can be sprayed, and the results are all fairly good. Southern blight: The southern blight pathogen overwinters in soil and on diseased plants. It is prone to occur between spring and summer, during the plum rain season, and in seasons with continuous autumn rain. When ventilation is poor, light is insufficient, and the potting medium is in an acidic state, the disease is especially severe. White mycelial lesions appear on the stems of diseased plants, and the lesions gradually expand to the whole plant, causing the pseudobulbs to rot, so that the leaves turn yellow and die. This disease infects rapidly and causes great damage. First, improve the above causes of disease. Second, at the early stage of onset, promptly repot, disinfect the diseased plants, and dispose of diseased plants that cannot be saved. Use sterile potting medium and pots. After potting, scatter quicklime or newly burned plant ash on the pot surface to adjust the acid-base balance, bring the soil to neutral and slightly alkaline, inhibit and kill the growth of pathogens, and prevent the recurrence of the pathogen. I once found three cases at an orchid friend's placeCymbidium ensifolium(large-leaf white) of southern blight. In one case, at a flower shop I found two pots displayedCymbidium ensifoliumfor sale, with white mycelium covering everything from the pseudobulb area to the leaf tips. The southern blight was extremely severe. I suggested he dispose of them, otherwise it would affect otherorchidsand flowers. In one case, at an orchid friend's home I found southern blight was also relatively severe. I proposed a treatment method: repot, use water soaked with newly burned plant ash to disinfect the plants, soak the plants in the plant ash solution for twenty minutes, at a high concentration (the ratio was not specified at the time, two large bowls of plant ash stirred into one washbasin of water), take them out to dry, and pot them using sterile potting medium and pots, then scatter a layer of plant ash on the pot surface. After treatment the effect was obvious, and the disease did not recur. In one case, at an orchid friend's home I foundCymbidium ensifoliumhad southern blight. I proposed a treatment suggestion: spray 1:2:150 Bordeaux mixture for sterilization, and scatter quicklime on the pot surface, without repotting. The effect was also quite good, and the disease did not recur. (Chen Jisheng)