How to prevent and control orchid pests and diseases? My observation records

After reading a few orchid books and growing a few pots oforchids, during thepractice of growing orchidsI discovered some phenomena not recorded in books or not quite consistent with book knowledge, and so I record them here. I. About spider mites Many books and periodicals have emphasized the harm of spider mites toorchids, but my observations over the past few years have found that spider mites actually do not like to attack orchid family plants; only when the population density on other host plants is extremely high, due to famine, do a small number migrate to the undersides of the tips of orchid leaves. Spider mites have diverse feeding habits, and common hosts include African daisy, Chinese rose, frangipani, citrus, red-flowered oxalis, lantern grass, and so on. I have visited several flower nurseries where, due to poor management, spider mites plagued Chinese roses, African daisies, and ornamental peaches endlessly, yet no spider mite damage was found on the adjacent Chinese orchids, Phalaenopsis, or Phaius. In my ownbalconyorchid growing, I had a similar experience. At that time there was a pot of frangipani; because it grew tall, it was inconvenient to inspect, and by the time I discovered it, almost all the leaf surfaces were packed with spider mites and webbing. In great alarm, I checked the orchid leaves and saw only scattered individual mites. After removing the frangipani and wiping it off by hand, it never recurred. In the courtyard, the ground-level red-flowered oxalis showed dense mite spots, while the orchid leaves showed no infestation. These phenomena suggest: 1. Chinese orchids are not ideal hosts for spider mites. 2. The primary measure for preventing and controlling spider mites is not to mix-plant or mix-place them with their common host plants; clear away ground weeds. II. About thrips. While spider mites seem to be inappropriately emphasized, on the contrary, thrips are often overlooked and not mentioned (so that many orchid growers have no awareness of thrips at all). In fact, the harm of thrips toorchidsis far more severe than that of spider mites, second only to scale insects. Adult thrips are 1.0-1.5mm long, dark brown, black, or ochre-yellow, move quickly, and can reproduce more than 10 generations per year. During the flowering period they damage flowers and flower stalks. Damaged flowers show yellow-brown spots, making plain-colored flowers look as if they have colored centers; when the petals and bracts are examined, the insects can be seen rapidly crawling deep into the flower center. In severe cases the petals wither, twist, tangle, or fail to open, and the fragrance is greatly reduced. During the non-flowering period they damage tender shoots; at this time the insects are extremely difficult to find, and only when the new shoots unfold their leaves are dense pale yellow spots found on the young leaves, easily mistaken for virus disease. As the young leaves grow, some of these spots turn brown-yellow or black; in severe cases the tender shoots die. Fortunately, thrips are not difficult to control; omethoate, Nongchongbi, and similar agents work very well. There is an orchid nursery in the Sanming area with several hundred thousand mu planted with orchids, harmed by thrips year after year, yet its owner was completely unaware. Orchid growers in the surrounding areas introduced seedlings from this nursery, and after planting, most of the new seedlings showed no similar symptoms. This phenomenon is somewhat puzzling, so I looked through some materials and only then clearly recognized thrips for what they are. III. About southern blight The occurrence of southern blight is closely related to the planting medium. Nowadays is an era when soillesscultivationis in fashion, yet some orchid growers still prefer planting in soil. I remember that when books introduced organic media they listed tree fern, pine needles, Chinese medicine dregs, rice husks, sawdust, wood shavings, tree bark, bagasse, crushed corn cobs, and so on. These media may carry fungi and insects, and strict disinfection can kill them, but this is not easy to do when planting on a large scale. On the other hand, when immature organic media encounter moisture they release some volatile substances such as methanol, acetaldehyde, tetrachloroethane, etc. These substances can stimulate the germination of dormant sclerotia of the small sclerotium fungus, thereby causing an outbreak of southern blight. The faster the organic medium decomposes, the more pronounced this releasing effect. Chinese medicine dregs especially have complex composition and are difficult to judge. I once tried Chinese medicine dregs in a corner where orchids were planted in the groundflowers - I remember they were mainly Shihu (the stems of the orchid family plant Dendrobium officinale) and others - and it happened to be a high-temperature rainy season, and these orchids soon died under the might of southern blight. The memory is still deep. IV. About anthracnose I once placed more than ten pots of orchids on the north balcony, mixed together with a pot of aloe. Later these more than ten pots of orchids contracted anthracnose, and it lingered without healing for more than half a year. After repeated pruning, I accidentally noticed that the aloe also had black spots on its leaves, and thought this was probably an important source of infection, so I discarded the aloe, again enlarged the cut, pruned the leaves, and sprayed pesticide, and this strange ailment was actually eliminated! From this I thought: to prevent and control pests and diseases, one should first clear away nearby sources of infection; and for some varieties with extremely poor resistance, should they be isolated and placed separately? I have recorded above these phenomena observed since I begangrowing orchids. Because of their one-sidedness and the particular background against which these phenomena occurred, they must absolutely not be taken as any kind of experience; the deeper theoretical essence of these phenomena awaits analysis, generalization, and summary by fellow orchid growers and experts. Xu Qinzhong Address: Yongchun County Hospital, Fujian Postal code: 362600