Why is orchid pest and disease control so difficult?

1. Determined by the special morphology of the orchid plant: Orchid roots are fleshy and prefer to live symbiotically with orchid mycorrhizal fungi. They require a slightly acidic substrate with good aeration and drainage. They are highly prone to root rot due to unsuitable substrate pH, poor aeration and drainage, poor water quality, or inappropriate fertilizer quantity and concentration. Once the roots rot, the supply line to the leaves is lost, and physiological diseases and reduced stress resistance will occur,pests and diseaseswill also take advantage and swarm in to cause damage. The plant, already weakened and diseased, has very weak transport function, making it difficult to deliver chemicals to the site of disease for the medication to take effect. Therefore, orchid pots should be rough in texture, with drainage and aeration holes at the bottom and sides. The growing substrate should be slightly acidic, rough and loose. The substrate should not dry out, and water and fertilizer should be easy to apply. Use soft water. Fertilizer concentration should be low, with intervals of more than half a month. For precious varieties, you can select some dragon roots (which should contain orchid fungi) from collected wild orchids, grind them into a thin slurry and pour it on to promote orchid root growth. Whenever leaf tips show scorching, it indicates that the orchid roots are diseased, and you should immediately repot, wash clean, remove affected parts, disinfect and replant. If you can occasionally spray American-made "Root Stimulant" and supplement with an appropriate amount of phosphorus fertilizer, it will be even more beneficial to healthy orchid root growth. The leaf sheaths (leaf buds or leaf scales) of orchids grow in overlapping layers, tightly wrapping the leaf base and serving to protect young leaves and support immature leaves. However, because they tightly wrap the leaf base, water from rain or watering/fertilizing can accumulate inside the tubular leaf sheath and is difficult to fully drain and evaporate for a long time, causing waterlogging damage. Water flow also naturally carries pathogens and small insects to the leaf base where they lurk and cause damage. Chemicals cannot easily reach there. Therefore, the leaf sheath is a natural ideal shelter and apartment forpests and diseases. Therefore, from the emergence of leaf buds until the leaf sheaths naturally dry and decay, closely monitor ventilation and light. When watering, fertilizing and applying chemicals, avoid directly pouring onto new buds and fresh leaf sheaths, and regularly spray fungicides to guard against leaf sheath rot. When leaf sheaths naturally dry and decay, remove them as thoroughly as possible to reduce hiding places forpests and diseases. Orchid plants grow in clusters, tightly packed together, with leaves standing at angles or curving downward, overlapping and covering each other. This is not conducive to ventilation and air movement, and also provides hidden dwelling places for pathogens and insects. Chemicals often cannot completely and thoroughly reach all areas.Orchid growersshould plant as sparsely as possible with wide, orderly spacing during display. When applying chemicals, extend the spray gun to the pot rim with the nozzle pointing upward, continuously lifting the spray gun while turning orchid leaves and spraying, then spray downward from the leaf surface, allowing the chemical to cover the plant base and underside. Pot rim. The orchid bench should also be repeatedly sprayed toward the ground and pot bottoms to ensure that pest and disease control chemicals reach everywhere, leaving no hiding place for pathogens and insects. Furthermore,orchidecological habits are largely contradictory and opposing, and it is not easy to properly grasp the dimensions of their organic unity. If the deviation is too great, physiological diseases will inevitably occur and stress resistance will weaken. Many people summarizeorchid growingas high shade, high temperature plus insulation, but this is precisely the condition for rapid reproduction and rampant damage by pathogens and insects. Therefore, one must dialectically understand and masterorchidecological habits and cultivate them according to their nature. Due to space limitations, I will not elaborate further here. Those interested, please refer to the "Orchid Garden" column in "Flowers and Bonsai" issues 2 and 3 of 1996, where my humble article "OrchidHabits Briefly Explained and Cultivation According to Their Nature" was published. 2. Incomplete elimination of infection sources 1.Orchid growingsites, old pots, growing substrates and production tools are mostly not disinfected. Even when disinfection is done, it is often just a formality: steaming time is too short, sun exposure time is insufficient, chemical concentration is too low, soaking time is inadequate, inevitably leaving hidden dangers. 2. Seed preparation, cleaning of debris and removal of diseased and residual parts are not thorough, especially for variegated orchids and high-grade varieties, where people are even more reluctant to excise diseased spots. Mostly, relevant chemicals are not selected specifically for the purpose and soaked for one hour for disinfection. Instead, cheap conventional fungicides are chosen, diluted at arbitrary ratios, sprinkled or briefly dipped for a moment, which simply cannot meet disinfection requirements. 3. Because the orchid plant morphology is rather special, and pathogens and insects invade precisely from their hidden parts, early symptoms are not obvious and not easily discovered. Once discovered, the damage from pathogens and insects is already near its peak. For example, sand spot disease on the underside of leaf tips is not easily detected on the leaf surface in its early stages. One must check the leaf undersides one by one to discover it. Scale insects also parasitize hidden areas and are not easily found in the early stages. In the early stages of pathogen invasion, there are no traces to follow and no color to distinguish, making it impossible to eliminate them. Even when disease spots are discovered, they are often on the leaf sheath and difficult to cut away. Therefore, before planting, thoroughly remove diseased and residual plant leaves and leaf sheaths and disinfect. After planting, when disease spots are found, cut them away early with appropriate excision, then apply chemicals for disinfection. Regular spraying and disinfection of the site, flower benches, pot bottoms and other environmental areas is also very important. 3. Improper control: 1. Failure to use the right medication for the condition: Orchidflowerdiseases are diverse and varied, not easy to accurately identify. Even if the disease can be identified, it is not easy to buy the corresponding specific treatment chemical. In particular, the instructions for many fungicides are greatly exaggerated, and with counterfeit and inferior drugs flooding the market, one simply does not know what to do, and has no choice but to keep using "zineb," "carbendazim" and "thiophanate." However, after prolonged and repeated use, resistance develops, and they have almost no control effect. It is best to use medication according to the condition: for physiological diseases, strengthen management and promptly correct deviations and provide rescue; for fungal diseases, use broad-spectrum fungicides; for bacterial diseases, use streptomycin and chloramphenicol; for mold diseases, use phytoalexin; for viral diseases, use antiviral agents; for scale insects, use insecticides with ovicidal function. Each chemical should not be used continuously more than three times; it is best to alternate several or use them in combination. 2. Improper chemical concentration. Every chemical has its safe and effective concentration. Too low, it cannot achieve the necessary killing effect; too high, it not only wastes but also easily causes chemical damage. It is best to choose a medium-to-upper concentration, and preferably dilute with soft water. Powder formulations should first be mixed with a small amount of water into a thin paste, then gradually diluted with more water. When mixing multiple chemicals, each should be diluted separately with one-third of the water amount, then mixed together, to prevent reduced effectiveness from mixing at high concentrations. 3. Improper intervals between chemical applications: Some people think that orchid plants have no pest or disease spots anyway, and have undergone various disinfection measures, so if no pest or disease conditions are found, there is no need to spray. Only when pest or disease conditions are discovered do they hurriedly apply chemicals. This approach of not implementing prevention as the priority but focusing only on treatment is inappropriate. Once it cannot be brought under control, losses are severe. The correct approach: for healthy plants, apply preventive chemicals once every half month; for those with a small amount of pest or disease conditions, apply once a week; when pest or disease conditions are severe, apply once every other day for three to four consecutive times, just as in vegetable pest and disease control, to effectively bring the pest and disease situation under control. 4. Improper method of control: Many people apply chemicals for control by just roughly spraying at the leaf surface. In this way, most pathogens and insects hidden on the leaf undersides and leaf sheaths do not come into direct contact with the chemical and simply cannot be eliminated. Instead, the pathogens and insects get trained in drug tolerance and form resistant populations, resulting in a situation where the problem cannot be cured for a long time, and even worsens with treatment. The correct approach: extend the spray gun into the leaf base area among the leaves, with the nozzle pointing upward and rotating left and right while spraying. Periodically lift the spray gun and turn the leaves so that the undersides of leaves that overlap and cover each other can all be sprayed. Pot rims, pot bottoms, orchid benches, pathways and surrounding environment should all be sprayed. Mist droplets must be as fine as mist and dew to effectively reach all leaf undersides, leaf surfaces and leaf sheaths. As for black rot, Phytophthora disease and root rot, their pathogens are not only on the plant leaves but also invade the roots. It is necessary to both spray and drench, working on both fronts simultaneously, for it to be effective. 4. Poor ecological conditions: Poor ecological conditions here naturally refers tocultivationmanagement conditions and facilities that still cannot basically meet the needs of orchid growth, which not only affects the orchid plant's own disease resistance but also provides conditions for the invasion, parasitism, reproduction and damage by pathogens and insects. This is undoubtedly an important reason for difficulty in control: 1. Overcrowding: Because greenhouses and sites are not cheap to build, in order to improve site utilization, people often plant and display too densely, or continuously increase the number of varieties, having to squeeze and cram them in. This inevitably affects ventilation and light, objectively providing good conditions for pathogen and insect invasion and reproduction. 2. Inadequate winter freeze protection: Many orchid growers still do not understand that frost damage to orchid plants is mainly due to the presence of "ice-nucleating bacteria" on the plants, which at low temperatures of minus 2 to 5 degrees can induce ice formation in plant cell water, thereby causing frost damage. Most do not take measures to inhibit and kill ice-nucleating bacteria, but only unilaterally seal and insulate. As a result, water vapor drips back onto the plant leaves, frost damage still occurs, and the orchid plants that did not freeze to death are nonetheless injured considerably, with greatly reduced pest and disease resistance. 3. Improper dry-humidity control. Many new orchid enthusiasts often cause root rot due to overly frequent watering. During the growing season, after watering and fertilizing, they hope for a higher germination rate while maintaining constant temperature, so they do not increase ventilation. This high humidity and high temperature is precisely a favorable condition for pathogen and insect reproduction and damage. In autumn and winter, in order to harden against cold and prevent the substrate from freezing, they withhold water too much, affecting healthy growth of orchid plants and weakening stress resistance. 4. Summer and autumn cooling and moisture retention not timely, measures ineffective. Doors and windows not opened in time, insufficient ventilation. Sometimes to cool down, well water or ice water with too great a temperature difference is used to water orchids, causing leaf margins and tips to scorch. Cooling should mainly be achieved by increasing shade layers (with 20 cm spacing between layers) and increasing ventilation, supplemented by generously sprinkling water at the orchid site. 5. Poor water seepage and aeration performance of orchid pots and substrate, leading to root rot, causing orchid plants to lose their supply line and greatly weakening stress resistance. Moss on the outer walls of orchid pots should be promptly removed. The substrate should be mixed with some wood shavings, tree fern, etc. as much as possible. Do not water too frequently. 6. Severe pollution: Orchid sites located in industrial areas, beside highways, or near coal-burning kitchens are susceptible to pollution from industrial waste gas and smoke, which not only affects healthy growth of orchid plants but also easily breeds pests and diseases. Measures such as shielding should be taken as much as possible. 7. Failure to pay attention to eliminating pest and disease transmission vectors. It is generally believed that insect pests are easy to find and easy to treat, so people only value the control of fungal diseases. Pests like scale insects, aphids, leafhoppers, flies, cockroaches and slugs, besides directly causing damage, also obligingly transmit fungal diseases. Attention should be paid to their control. 8. Over-application and excessive application of nitrogen fertilizer: Often, in pursuit of a higher germination rate and dark green leaf color, people over-apply and excessively apply nitrogen fertilizer, causing leaves to become overly tender and reducing disease resistance. 5. Low immune function: Due to division propagation, extensive use of chemical fertilizers, growth promoters and winter-spring insulation and bud forcing, orchid plants fail to properly undergo vernalization, greatly reducing their immunity. It is recommended that during the new bud leaf-unfolding stage, spray once with a 1000-fold dilution of German-made "Phytol 20003" to provide orchid plants with a sufficient and balanced nutrition, inducing orchid plants to enhance resistance to physiological disorders and resistance to fungi, bacteria and viruses. At the same time, spray once a month with a 1000-fold dilution of the medical antipyretic-analgesic "aspirin (A, P, C acetylsalicylic acid)" to act on the orchid plant's genetic genes, inducing the production of specific messenger RNA, which is then translated into various proteins related to the orchid plant's disease resistance, to block pathogen invasion, spread, and kill or inhibit their growth, thereby increasing immunity. Now that the reasons for difficulty in prevention and control are known, one can maximize strengths and avoid weaknesses, strive to avoid extremes, and advance despite difficulties. May everyone's orchids grow robustly! (Xu Dongsheng)