Why are the diseases and insect pests of orchids so difficult to control?

1. The particularity of the morphology of the orchid plant:

The root of orchid is fleshy and likes to symbiosis with orchid fungus, and it needs a substrate with good acid, air permeability and hydrophobicity, and it is very easy to rot the root because of the discomfort of pH, air permeability and hydrophobicity of the culture medium, or because of poor water quality and unsuitable concentration of fertilizer. As soon as the root is rotten, the supply line of the plant and leaf will be lost, physiological diseases and stress resistance will be weakened, and diseases and insect pests will also take advantage of the deficiency and swarm to do harm. This is a sick and weak residue, and the transport function is very weak, so it is difficult to transport drugs to achieve the effect of the disease.

Therefore, the texture of the orchid basin should be rough, the bottom and edge should be rich in breathable and hydrophobic holes; the peilan matrix should be sour and rough, loose, the matrix is not dry, easy to apply water and fertilizer, use straight soft water; the concentration of fertilizer should be low, and the interval should be more than half a month. If it is a precious variety, you can select part of the dragon root (suitable for orchid bacteria) from downhill, grind it into a slurry and cast it to promote the growth of orchid root. All those with scorched leaf tips suggest that Langen is sick, that is, they should be pots, washed, removed, disinfected and replanted as soon as possible. If American products can be sprayed occasionally to "promote root growth", and appropriate amount of phosphate fertilizer can be added, it is more conducive to the healthy growth of Langen.

The leaf sheath of orchid (leaf trousers or leaf beetle), stacked and long, tightly wrapped around the leaf base, plays the role of protecting young leaves and supporting immature leaves, but also because it is tightly wrapped in the leaf base, it is easy to be silted in the tubular leaf sheath when Rain Water or irrigating and spraying fertilizer, which is difficult to be fully excreted and evaporated for a long time, and has the disadvantage of waterlogging, but also with the flow of water, naturally drives germs and bugs to migrate to the leaf base and lurks to harm. The potion is not easy to reach. Therefore, the leaf sheath is a natural ideal shelter and apartment for diseases and insect pests.

Therefore, from the time the leaf bud is exposed to the natural drying and decay of the leaf sheath, pay close attention to ventilation and light transmission, avoid pouring water, fertilizer and liquid medicine directly into the new bud and fresh leaf sheath, and spray fungicides regularly to prevent the leaf sheath from rotting; when the leaf sheath is naturally dry and rotten, it should be removed as far as possible to reduce the hidden ground of diseases and insect pests.

The orchid plants grow in clusters, the clusters are close to each other, and the leaves are oblique and drooping, covering each other, which is not only disadvantageous to ventilation, but also provides a hidden shelter for bacteria and insect pests. Orchids should be sparsely planted as far as possible, spaced and displayed in an orderly way. when applying, the spray gun is extended to the edge of the basin, the nozzle is facing up, and the spray gun is constantly raised, turning the orchid leaves, spraying at the same time, and then spraying downward from the leaves, so that the chemicals spread the plant base and negative. The edge of the basin. The orchid frame should also be applied to the site and the bottom of the basin repeatedly to ensure that control agents are involved everywhere and that there is no place to hide bacteria and insect pests.

In addition, the ecological habits of orchids are mostly contradictory and opposed to each other, so it is not easy to properly master the size of its organic unity. If it is biased too much, it is bound to develop physiological diseases and weaken stress resistance. Many people sum up orchid cultivation as high overcast and high temperature plus heat preservation, which is the condition for the rapid reproduction of bacteria and insect pests and wanton damage. Therefore, we must dialectically understand and master the ecological habits of orchids and cultivate them according to nature. Due to the limitation of space, I will not repeat it here. For those who are interested, please refer to the second or third issue of Flower and Tree Bonsai 1996, Orchid Garden column, my clumsy work, "Orchid habits and dependent cultivation".

Second, the source of infection is not completely eliminated.

1. Most of the sites, old pots, culture media and production tools of orchid cultivation are not sterilized. Even if there is disinfection, it is mostly a mere formality, the cooking time is short, the exposure time is less, the concentration of the agent is too low, and the soaking time is insufficient, which leaves hidden dangers.

2. Clean up the seeds and get rid of the disease and disability. The decayed part is not complete, especially the line art orchid and high-end products, even more reluctant to expand the plaque. There is no targeted selection of corresponding agents, soak for an hour to disinfect, mostly choose cheap conventional fungicides, any multiple dilution, dripping wine or slightly dipping in for a while, can not meet the requirements of disinfection at all.

3. Because the shape of the orchid plant is special, and the bacteria and insect pests invade from its hidden parts, the early symptoms are not obvious and are not easy to be found. once found, the damage of bacteria and insect pests is close to the peak. Like the sand spot on the back of the leaf tip, it is not easy to detect the disease on the leaf surface in the early stage. You need to check the back of the leaves one by one to find out. Scale insects are also parasitic in hidden places and are not easy to detect in the early days. To the early stage of bacterial invasion, there is no trace to follow, colorless, can not be stopped at all, even if the disease spot is found, it is often on the leaf sheath, difficult to cut off. Therefore, the leaves and leaf sheaths of diseased and residual plants should be thoroughly removed and disinfected before planting. After planting, the disease spot is found, the disease spot should be cut off as soon as possible and expand the wound properly, and then disinfect it with medicine. Frequent spray disinfection of sites, flower racks, pot bottoms and other environments is also very important.

Third, improper prevention and control:

1. Failed to use drugs for symptoms: orchids have a variety of diseases, and it is not easy to accurately identify them. Even if they can identify diseases, it is not easy to buy corresponding attending drugs. In particular, the descriptions of many fungicides have been exaggerated, coupled with the fact that fake and inferior drugs have flooded the market, leaving them at a loss as to what to do, so they have no choice but to use "Dysen zinc", "carbendazim" and "topiramine". However, it has been commonly used and repeatedly used for a long time, resulting in drug resistance and almost no control effect. It is best to use symptomatic drugs: physiological diseases to strengthen management and timely correction and rescue; fungal diseases, with broad-spectrum fungicides; bacterial diseases, with streptomycin and chloramphenicol; neophytomycin for fungal diseases; antiviral agents for viral diseases; therefore, shell insects, the application of insecticides with egg-killing function, and the continuous use of each agent, no more than three times, it is best to use several kinds of pesticides alternately, or mixed.

2. Improper concentration of the drug. The powder should first be mixed with a small amount of water to form a dilute paste, and then gradually diluted with water. When a variety of agents are mixed, they should be diluted with one-third of the water, and then mixed to prevent the high concentration of mixing and reducing the effect.

3. The interval of application is inappropriate:

Some people think that the orchid plant does not have any disease and insect spots, and after many aspects of disinfection, there is no need to spray if there is no disease and insect disease. It was only when diseases and insect pests were found that the medicine was applied in a hurry. It is not appropriate to put prevention first and focus only on treatment. If you can't hold it down, you will lose a lot of money. Should be, healthy plants, once every half a month to prevent, already have a small number of diseases and insect pests, once a week, when the disease and insect pests are serious, should be like vegetables to prevent and control diseases and insect pests, once every other day, continue three or four times, in order to effectively control the disease and insect pests.

4. Improper methods of prevention and control:

Many people apply medicine to prevent and cure it, but just shoot roughly at the foliage. In this way, most of the bacteria and insect pests hidden in the leaf back, leaf sheath, do not have direct contact with the medicine, can not eliminate it at all, but let the bacteria and insect pests get drug-resistant training and form a drug-resistant population, resulting in long-term treatment, or even the more serious consequences of cure. It should be that the spray gun is put into the base of the leaves, and the nozzle is turned upward and left and right to spray. Lift the spray gun from time to time and turn the blades so that the backs of the leaves that cover each other can be sprayed. The edge of the basin, the bottom of the basin, the orchid shelf, the passageway and the surrounding environment are sprayed. Fog point, must be as thin as fog dew, in order to effectively spray all leaf back, leaf surface, leaf sheath.

As for black rot, blight and root rot, the pathogens are not only in the plant leaves, but also invade the roots, so it must be sprayed and poured together to be effective.

Fourth, the ecological conditions are poor:

The poor ecological conditions mentioned here naturally refer to the conditions and facilities of cultivation and management, which can not basically meet the needs of orchid growth, which not only affects the disease resistance of orchid plants, but also provides conditions for the invasion, parasitism, reproduction and damage of bacteria and insect pests. This is undoubtedly an important reason why it is difficult to treat:

1. Overcrowding: because the cost of shed and site is not low, in order to improve the utilization rate of the site, it is often too dense to plant, display, or constantly increase the number of varieties, so we have to squeeze it. It is bound to affect ventilation and light transmission, and objectively give the invasion of bacteria and insect pests. Reproduction provides good conditions.

2. Ineffective anti-freezing in winter: many orchid farmers still do not understand the freezing damage of the orchid plant, mainly due to the existence of "ice nucleation bacteria" in the orchid plant, which can induce water freezing in plant cells at a low temperature of minus 2 mi 5 degrees, thus causing freezing damage. Instead of killing ice nucleation bacteria, they only unilaterally sealed and kept warm. As a result, water vapor dripped back on the leaves of the plant, resulting in ice damage. The orchid plant that did not freeze to death would be seriously injured and its resistance to diseases and insect pests would be greatly reduced.

3. Improper control of dry and humidity. Many new orchid friends often rot their roots because they are watered too frequently; during the growing period, after watering and fertilizing, they hope to have a higher germination rate in order to maintain a constant temperature and do not increase the ventilation rate. This, high humidity and high temperature, is a good condition for bacteria and insects to reproduce and do harm. In autumn and winter, in order to resist the cold and prevent the culture medium from freezing, the water was deducted too much, which affected the healthy growth of the orchid plant and weakened the resistance.

4. The cooling and moisturizing in summer and autumn is not timely, and the measures are not effective. The doors and windows are not opened in time and the ventilation is insufficient; sometimes in order to cool down, the well water or ice water with excessive temperature difference is used to irrigate the orchid, resulting in the focal edge of the blade. Cooling should mainly increase the shade layer (there should be a 20 cm interval between the layers), and increase ventilation, supplemented by a large amount of water spraying in the orchid field.

6. Serious pollution: Lanchang is located in the industrial zone, beside the road or near the coal-fired kitchen, which is easy to be polluted by industrial waste gas and soot, which not only affects the healthy growth of orchid plants, but also prone to diseases and insect pests. Measures such as occlusion should be taken as far as possible.

7. Did not pay attention to extinguishing the vector of bacteria and insects. It is generally believed that insect pests are easy to find and easy to treat, but only pay attention to the prevention and control of bacterial diseases. Pests such as mosquito shells, aphids, leafhoppers, flies, cockroaches and slugs, in addition to direct damage, are also duty-bound to spread bacterial diseases, and attention should be paid to prevention and control.

8. Partial application of more nitrogen fertilizer: in order to have higher germination rate and thick green leaf color, more nitrogen fertilizer was applied, resulting in too young leaves and decreased disease resistance.

Fifth, the immune function is low:

Due to disassembly and reproduction, extensive use of chemical fertilizers, growth promoters and heat preservation and budding in winter and spring, the orchid plant could not be vernalized normally, resulting in a great decline in the immunity of the orchid plant. It is suggested that "Plant Animal 20003" produced by 1000 times liquid German should be sprayed once in the new bud and leaf expansion stage, so as to provide sufficient and balanced nutrition to the orchid plant and induce the orchid plant to enhance its ability to resist physiological obstacles, fungi, bacteria and viruses. At the same time, aspirin (A, P, C acetic acid salicylic acid) was sprayed once a month with 1000 times liquid medical antipyretic analgesics to act on the genetic genes of orchid plants and induce the production of specific messenger RNA, which was then translated into a variety of proteins related to the disease resistance of orchid plants to prevent the invasion and spread of pathogens and to kill or inhibit their growth so as to increase immunity.

Knowing that it is difficult to prevent and cure, we can make full use of our strengths and avoid weaknesses, avoid biases, and move forward in the face of difficulties. May your orchids thrive! (Xu Dongsheng)