Three key measures to grasp in orchid disease prevention

Orchid diseases mostly begin with soggy, stuffy, unclean substrate or with substrate that is too dry. When the substrate is soggy, stuffy and unclean, air is pushed out, pathogens multiply in great numbers, orchid roots are damaged, and various diseases arise from this, harming the orchid plant. When the substrate is too dry, the fleshy roots, after physiological water loss, shrivel and lose their conducting ability, so water and nutrients cannot be supplied in time, and orchid leaves become rough with scorched tips. An orchid plant struggling on the edge of life and death will, in order to stay alive, open its stomata wide to absorb moisture from the air, and various pathogens take the opportunity to invade, with disease following. In addition, if the concentration of fertilizer or pesticide is too high, exceeding the cell concentration of the orchid plant, it causes reverse osmosis and makesorchid grasslose water, which likewise triggers disease. To preventorchiddiseases, besides measures such as keeping the environment clean and moist, ventilated, watering and fertilizing lightly and evenly, applying pesticides at the right time and in the right amount, keeping the substrate clean and permeable, and providing suitable light, one must, even more, according to the actual conditions of each place, grasp the main contradiction and carry out targeted prevention and control. In the Jiangsu-Zhejiang area, the plum rain season has warm weather and high air humidity; it is the golden season fororchid grassgrowth during the year, and also the peak period for various diseases. Based on the author's many years of observation, various diseases are most likely to occur when the temperature is around 22 degrees. To avoid disease, two things must be done in this season: first, control watering; second, apply pesticide in time. In autumn, the climate turns from hot to cool, and this is another growing season fororchid grass. Autumn air is relatively dry, and orchid grass easily loses water, so attention must be paid to timely watering. At the same time, after passing through the hot summer, orchid grass has consumed a great deal and its resistance is relatively weakened, so in early autumn phosphorus and potassium fertilizer should be supplemented in time to strengthen disease resistance. Autumn is also a peak period for various diseases, so pesticide must be applied in time. During the period from one week before the Start of Autumn to Cold Dew, pesticide must be applied to orchid grass once every ten days, to ensure that orchid grass can grow healthily throughout the whole autumn and until the spring of the following year. In winter,orchidneeds to be kept warm and brought indoors. Some people build sealed plastic sheds on an indoor balcony or under a wind-sheltered, sun-facing eaves, and place the potted orchids inside to receive sunlight. Sometimes the temperature inside the shed rises to over twenty degrees, letting them be steamed stuffily, and disease spots occur from time to time. Once discovered, applying medicinal liquid to the leaf surface is of no help anymore. With closed plastic sheds, including glass sheds, one must always be careful; once the temperature inside the shed exceeds ten degrees, windows must be opened in time and the film opened to let the orchids ventilate. When encountering weather with high temperature and strong sunlight, appropriate shading is also needed; never expose them to blazing sun and steaming. The lateorchid growingmaster Mr. Wang Shuping of Yuyao pointed this out emphatically in his article "Talks on Fifty Years of Orchid Growing Experience," saying, "Orchid growers often overlook this point, so special reminder is needed." In summary, fororchid growingin the Jiangsu-Zhejiang area, on the basis that other management measures can all keep up in time, controlling watering and applying pesticide in time during the plum season; watering in time, supplementing phosphorus and potassium, and applying pesticide at the right time in autumn; and avoiding blazing sun and steaming in winter are the keys to disease prevention and treatment in the different seasons. Grasp these three key seasons when disease easily occurs, and the disease prevention effect will be very different. As for the high-temperature season, because the temperature is too high, disease is not obvious, and doing a good job of ventilation and shading is enough. In addition, the layout and treatment of the substrate also require much attention. In the orchid pot, the substrate should be coarse below and fine above, with clear layers, so that water is received evenly. Substrates of different coarseness are best not mixed together for planting orchids, lest when watering, because large particles block the way, water is distributed unevenly, causing orchid roots that receive too much water to rot and orchid roots that receive too little water to shrink dry. Before planting orchids, the substrate must be disinfected; it can be sun-dried, steam-sterilized, or stir-fried in a pot. The purpose is to kill pathogens and eliminate the disease sources inherent in the substrate. Yu Zongying