Prevent pathogen transmission during vegetation shading

In order togrow orchids, people truly try every possible means, using every corner: balconies, windows, and so on. They wish they could replace even the bridal bed in the boudoir with orchid shelves, or throw out the basins, bowls, pots and stoves and neatly arrange rows and rows of orchid pots. At such times, one cannot help but miss the large courtyard of the old family home covered in green moss. If it were filled withorchids, with a few large trees in the courtyard providing protection, all the worry of shading the orchids every day would be saved. In a word, this godforsaken place in town makesgrowing orchidsreally exhausting. If in a park, or on some patch of green space, with pines, firs, willows and poplars lush and verdant, deep and elegant, continuous and unbroken, alternating thick and thin, green leaves, blue-green grass, and when wind blows, coolness over the whole body. I generally will not stare fixedly at the frozen young men and women like Western sculptures among the trees; I will keep touching this leaf and pinching that tree trunk. In my heart I keep praising: how great this place would be for me togrow orchids! How many pots could be placed here. Having large trees for shade is of course good: it forms a microclimate, with high humidity, low temperature, purified air, wind protection and noise reduction, known as natural air conditioning. If some orchid enthusiast has a courtyard of their own, with lush trees and orchid pots placed below, that is truly the envy of others. With a big tree at one's back, one can enjoy the shade; for open-air orchid growing, planting small trees and shrubs around can effectively lower the temperature and create a suitable environment fororchids. With casual management, the orchids also live well and moistly, unlike us whogrow orchids on balconies, where shade netting blocks sun but not heat, and the preciousorchidsare scorched and battered, dry one moment and wet the next, busy rushing in circles, such worry. However, although tree shading for courtyard orchid growing is good, a courtyard is not nature. In the orchid's native habitat the ecology is balanced, and all things generate and restrain one another, so all is peaceful. In human dwellings, the ecology is single and unbalanced, with more or less a small amount of disease; would it not be better to prevent it a little. Most trees carry pathogens and pests. Although trees are woody and orchids are herbaceous, both are plants; though each has differences, they are largely the same with minor differences. If pathogens complete incubation, and spores complete the process of production and spread, and the number of diseases accumulates to a certain degree, the pathogens go from latent period to infectious period, and if they encounter suitable climate and environment, they may cause harm to orchids. One must remember the eight words: "prevention first, integrated control." When orchid enthusiasts apply chemicals, it is also not a bad idea to conveniently spray the small trees and other flowers near the orchid pots. Some pathogens are extremely infectious. They transmit through vectors (mainly insects, especially aphids and leafhoppers most commonly, followed by soil nematodes and fungi). Next, they transmit through pollen; pollen often carries viruses, and thus pathogens can be spread through pollen. Viral diseases are mostly systemic infections, with no disease signs, and are easily confused with non-infectious diseases; their infectivity often needs to be confirmed through transmission tests by a certain method. The transmission modes of plant viral diseases include: mechanical (rubbing) contact transmission, grafting transmission, vector (including insects, nematodes, fungi, mites and dodder) transmission, pollen and seed transmission, etc. Since viruses are obligate parasites, their sources of infection are all related to living bodies (living animal or plant bodies or vectors); transmission requires the virus to contact a living body. For example, for sap rubbing inoculation, fresh virus sap must be used; the purpose of rubbing is to cause micro-wounds on the surface of the host plant body, so that the virus may enter living cells. Excessive injury causes tissue necrosis and is not conducive to virus transmission. The way aphids, planthoppers and other piercing-sucking mouthpart insects feed on plant sap more easily satisfies the two requirements for plant virus spread. Usually, orchid enthusiasts like to use vines to form a trellis and place orchid pots below. If it is grapes, one needs to be careful; grapes are prone to black rot, gray mold, brown spot, etc., especially anthracnose, which is severe. If the environment is not ventilated and the temperature is 29-35°C, the disease develops quickly. I have had lessons about this. In grape-producing areas, fruit farmers apply chemicals once every ten days and carefully guard against it to protect leaves and fruit; this anthracnose breaks out severely, and if there is any negligence, losses are heavy. Plant fungal diseases have reached more than 30,000 species, accounting for 80% of plant diseases. About 200 species of plant bacterial diseases are known. Several trees are easily infected. Chinese fir often develops bacterial leaf blight; in general plantations the incidence rate is above 50%, and in severe cases can reach 100%. Chinese fir anthracnose is common in the Jianghuai hilly region of Anhui. Poplar black spot disease can make poplar leaves turn black, dry up, and fall fluttering like Liang Shanbo and Zhu Yingtai turning into butterflies. If orchid pots are placed under the trees, one must prevent these tree leaves from falling onto the flower pots, so as to avoid transmission. Plane trees mainly develop anthracnose; the disease mostly occurs on leaves, petioles and tender shoots. Symptoms include dot-like chlorosis on leaves, gradually expanding, with the center of the lesion rupturing, diseased leaves falling early, and in severe cases causing leaves and tender shoots to die. This disease belongs to Deuteromycotina, genus Colletotrichum, and spreads through wind, rain, etc. Plane tree longing rain, plane tree night rain, autumn colors reach the empty boudoir, at night sweeping plane tree leaves. Plane trees plus fine rain, until dusk, drop by drop. Rustling rain on plane tree leaves. What a beautiful realm! Yet in this Song ci poetic imagery lurks killing intent; if one is not careful, orchids suffer invasion, and therefore one should be cautious. When growing orchids in open areas, one should note keeping away from tobacco, medicinal plants, etc. Tobacco is the most severely diseased among crops; according to reports, the damage rate reaches 64%. Worldwide tobacco diseases include more than one hundred parasitic and non-parasitic diseases. In China there are nearly 20 major diseases, with mosaic disease and anthracnose being more severe. Medicinal plants suffer black spot, rot, leaf spot, root rot, anthracnose, etc. The pathogen types are somewhat similar to orchid pathogen types, and attention must be paid to prevention. Chinese pine, citrus, Bischofia polycarpa, Pittosporum tobira, poplar, etc. are susceptible to sooty mold. When the leaves, tender shoots and branches of the above trees are covered with soot-like matter, tree photosynthesis is weakened, and in severe cases causes withering. Courtyard orchid placement should pay attention. Tea tree diseases: about 30 species are common in China, and the pathogens are mostly fungal diseases, among which cloud-pattern leaf blight, anthracnose, white star disease and black spot disease are more common, with high incidence. Orchid growing should also stay away from this. Ornamental plant diseases: some orchid enthusiasts like to place orchids together with other flowers to increase air humidity. But some ornamental plants are prone to disease, such as: rose black spot, chrysanthemum brown spot, camellia anthracnose, clivia bacterialsoft rotdisease, evergreen anthracnose, jasmine southern blight, clivia southern blight, etc. If discovered, throw them away quickly, then spray orchids for protection. Pests: open environments are more likely to suffer pests. Various pests, when unprotected or lacking natural enemies, are resolute and decisive, striding like tigers and wolves, raising sharp spines to show strength, secreting poison to display ferocity. They either suck sap or bore and eat leaves. There is a kind of jujube inchworm; during major outbreaks it can eat all the leaves of a whole tree. Various pests not only bring physiological harm, but also transmit pathogens, which is even worse. Under dry weather conditions, trees sometimes develop mite damage, extending to orchid pots, causing orchid leaf chlorophyll to be destroyed. Mites can complete 1 generation in about 5 days above 30°C, with severe damage. The pathogens of plant diseases are biological pathogens (organisms that can cause plant disease are called pathogenic organisms, or pathogens for short, including fungi, bacteria, mycoplasma-like organisms, rickettsia-like organisms, viruses, viroids, nematodes and parasitic seed plants, etc.). Diseases caused by them are all infectious, called infectious diseases or parasitic diseases. They harm orchids through the contact period and invasion period; invasion methods include direct invasion and invasion by external force. Rainy and humid conditions that favor the formation of water droplets are favorable for the invasion of such pathogens. Plant diseases can be divided into three kinds: (1) Fungal diseases. Fungal diseases are the most important category among flower diseases. Fungi are lower plants without chlorophyll and cannot be seen with the naked eye. They cannot manufacture nutrients themselves and absorb nutrients within the flower plant through mycelium. Fungal spores spread everywhere by wind, rain, insects, etc. (2) Bacterial diseases. Bacteria are very small single-celled organisms, without differentiation of vegetative and reproductive bodies; they absorb nutrients through the cell membrane and reproduce by division. Bacterial infection mainly occurs through stomata, nectaries, wounds and other routes, and is generally spread by flowing water, wind and rain, insects, soil and diseased plant residues. (3) Viral diseases. Viruses are extremely tiny parasites, visible only with an electron microscope, and viruses reproduce only in living flower cells. Viruses spread through insects (mainly piercing-sucking mouthpart insects, such as aphids, red spiders, etc.), mechanical injury and other routes. Various pathogens rely on various interrelationships among organisms, such as predation, parasitism, competition and mutually beneficial symbiosis, to survive. We know that among plant diseases, about 70-80% are caused by fungi. Among plant infectious diseases, fungal diseases are the most numerous, accounting for more than 70-80% of all plant diseases. Every crop will be attacked by several to dozens of fungi. Diseases caused by biological pathogens such as fungi and bacteria are contagious and are called infectious diseases. Anthracnose, bacterial diseases, etc. often occur in high-temperature and high-humidity environments, while gray mold occurs under cool, humid climates, and powdery mildew is more likely to occur in poorly ventilated facilities forcultivation. If the orchid growing site has sufficient light, air circulation and a clean surroundings, pathogens will not easily invade. Generally speaking, plant pathogen and virus symptoms can be roughly divided into the following types: 1. Discoloration: includes the 3 types "mosaic," "mottling" and "color breaking." "Mosaic" refers to light and dark green alternating patches appearing on diseased leaves. "Mottling" refers to chlorotic spots on diseased leaves, with spots relatively large, edges not obvious, and distribution uneven. The phenomenon of "discoloration" expressed on petals is called "color breaking." 2. Chlorosis and yellowing: the whole plant or some organs appear light green or yellow. 3. Spots and stripes: often occur on leaves, stems, fruits and other parts, appearing as necrotic spots, necrotic stripes, chlorotic spots or chlorotic stripes. 4. Ringspot and oak-leaf pattern: both mostly appear on leaves. Concentric ring-shaped spots are called "ringspot." Oak-leaf-shaped discoloration patterns along leaf veins are called "oak-leaf." 5. Vein clearing, yellow veins and vein banding: vein clearing and yellow veins are the early stages of mosaic symptoms. First the leaf veins become transparent, called "vein clearing"; then the leaf veins turn yellow, called "yellow veins"; "vein banding" is dark green discoloration along leaf veins. 6. Leaf wrinkling and leaf curling: deformation of local tissues or organs. Leaf vein growth is inhibited while leaf mesophyll still grows, leaves become wrinkled, and leaf margins curl upward or downward. 7. Clustering and dwarfing: the terminal buds of diseased plants are inhibited, lateral buds sprout abundantly, and branches cluster, called "clustering" or "rosetting." Internodes shorten and the plant uniformly becomes shorter, called "dwarfing." 8. Enations: protrusions produced on leaf veins on the underside of diseased leaves, shaped like ears, called "enations." Therefore, if we find that surrounding vegetation in the orchid growing environment has the above symptoms, we should consider taking measures to prevent orchids from being infected. Disease quantity is a developmental process from few to many, and distribution from point to surface. Within a suitable season, various diseases develop at different speeds, and their rates of increase differ; even for the same disease, its quantity growth speed and extent vary due to various conditions. The differences in the appearance of disease occurrence come from the characteristics of the disease itself, including whether there is reinfection and how many generations, the level of reproduction and mortality rates, and the efficiency of transmission and other factors. Even when the amount of inoculum is very low, some diseases will cause a certain degree of harm as long as conditions are suitable, while other diseases may not cause a major epidemic even if conditions are suitable; such diseases cause harm only when the amount of inoculum is relatively large. Different diseases require different amounts of time for the inoculum accumulation process. Some diseases can complete the inoculum accumulation process within a single growing season as long as conditions are suitable, causing epidemic transmission and harm of varying degrees. We can also see that disease transmission and reinfection are mostly aboveground diseases, local diseases, and also some systemic diseases; transmission modes are mostly airborne and spread by wind, rain and flowing water, and also insect-borne. The transmission distance and efficiency are generally relatively large. Moreover, wind and rain not only break orchid leaves, but also splash pathogen-bearing soil from the pot surface or the ground onto the orchid crown or orchid leaves, leading to brown rot in the plants. As the proverb says: place potted orchids on shelves, do not place them on the ground. Besides ventilation, it is probably also because during heavy wind and rain, pathogen-bearing soil on the ground splashes onto orchid leaves. . Pathogens often have relatively long lifespans and strong resistance to adverse environments. Apart from being easily affected by the environment during the invasion period, once invasion succeeds, they are affected very little by environmental conditions; therefore, disease epidemics are less governed by the environment. When the amount of pathogen inoculum is small and disease occurrence is sporadic, it is easily overlooked. Once the inoculum accumulates to a certain level, and then susceptible varieties are encountered and the climate favors invasion, severe harm will occur, and loss becomes certain. Therefore, do not treat it lightly. For some diseases, the overwintering inoculum source successively contacts hosts, and the infection time is drawn out longer, with disease occurrence earlier or later. In fact, any plant disease always requires a certain time after host infection before producing progeny inoculum. From infection to transmission, there is a lag time: the latent period. It is known that some pathogens can remain latent for several years and will come back again when conditions are suitable. Therefore, initial inoculum sources should be eliminated, harm should be reduced throughcultivationmeasures and chemical application, etc., and doing good orchid garden hygiene and disinfection can achieve good results. At the same time, one should take a long-term view and adopt effective measures to prevent inoculum accumulation and nip trouble in the bud. Diseases caused by pathogen infection are called infectious diseases. The factors causing them include pathogens, susceptible plants, environmental conditions and human factors. When pathogens infect plants, the plants do not necessarily become diseased; whether disease occurs also depends on the strength of the plant's disease resistance. If disease resistance is strong, disease will not occur or will be very mild. In a word, when orchids are grown strong and their resistance is strong, diseases will be reduced. In summary, using trees to shade orchids has advantages and disadvantages. Overall, the advantages outweigh the disadvantages: trees can lower temperature and increase humidity. The only thing to note is preventing tree vegetation from being infected by pathogens and thereby bringing disaster to orchids. In courtyards, be mindful that high walls block wind, causing poor air circulation and increasing opportunities for pathogen occurrence. (Kuai Xue Shi Qing)