high temperature and humidity

At the height of summer, humidity and temperature rise sharply, and orchids enter the peak reproductive season. Watching the orchid sprouts grow angrily every day, I feel more or less the joy of harvest. I believe that Orchid friends will watch it several times a day. Observe their growth carefully. The occurrence of diseases will inevitably affect the mood.

In fact, the meteorological conditions of high temperature and humidity are conducive to the occurrence of diseases, high temperature changes the physical and chemical properties of protoplasts, reduces the dispersion of biological colloids, a large number of electrolytes and non-electrolytes exosmosis, esters become layered, and sometimes lead to the destruction of cell structure, making the nucleus dilated, loose and cracked. High temperature also changes its respiratory intensity, which hinders the synthesis of plants, and the decomposition of protoplast is greater than synthesis, especially when the light is insufficient and the temperature is too high. In our management, we always pay attention to and strengthen our defenses. In line with the plant protection policy of focusing on prevention and control, early treatment, small treatment, treatment. Lest a year of toil be ruined by carelessness.

In order to prevent orchid diseases, in addition to keeping the environment clean and humid, ventilated, watering and fertilizing light and evenly, timely and moderate use of medicine, clean and transparent matrix, suitable light and other measures, but also according to the actual situation of various places, grasp the principal contradiction, targeted prevention and control. Hot and humid climate in midsummer, high air humidity, bluegrass is the golden season for the growth of the year, but also the prevalence of various diseases. In order to avoid diseases, we should pay attention to two points: one is to control watering, and the other is to apply pesticide in time.

If the matrix is wet and unclean and too dry, the air is squeezed out, the bacteria multiply in large numbers, the orchid root is damaged, and various diseases occur, harming the orchid plant. The orchid plant, which is struggling on the line of life and death, will open its stomata to absorb water from the air in order to maintain its life. all kinds of germs take advantage of the deficiency, and the disease occurs subsequently. The orchid grass degree is very hot, the consumption is large, and the resistance is relatively weak. some think that in the high temperature season, the disease is not obvious because of the high temperature, so it is necessary to do a good ventilation and shade. Actually, no. At present, it is in the season of high humidity and high humidity, which is the period of high incidence of flower diseases.

The main routes of transmission are as follows: 1. The pathogen invaded from the wound due to the man-made mechanical trauma of the plant. When encountered with a high temperature of 27 ℃ and 30 min, coupled with poor ventilation and poor drainage, the disease occurred and developed rapidly. two。 It is an insect infection in which flower plants are bitten by insects. 3. Is the flower growth environment has not carried on the thorough sterilization and so on the factor, easy to infect the disease.

In case of long drought, high temperature and sudden drop in heavy rain, the temperature drops suddenly, and the increase of substrate humidity leads to the prevalence of bacteria. In rainy season, attention should be paid to the prevention and control of common diseases such as black spot and anthracnose. Methyl topiramate, carbendazim and Huakang No. 2 can be used alternately before or after the mildew season. Spray foliar once every 10 days. If the occurrence of insect pests, such as Huakang No. 1, enemy killing and other appropriate medicine, timely treatment.

In our peacetime management, first, we should pay attention to ventilation, lighting, and drainage to create a good environment; second, we should cultivate strong orchid seedlings to enhance their resistance to diseases; and third, we should strictly quarantine and disinfect to prevent the spread of foreign germs and insect pests. In the future, pesticides should be sprayed regularly to eliminate diseases and insect pests before being victimized. Before planting, it is necessary to strictly disinfect orchid plants and plant materials, so as to reduce and put an end to mechanical injuries and contact infections caused by insects and humans.

The knives and scissors we often use should be sterilized before use. Disinfectants can generally be disinfected with 0.1% potassium permanganate, 5% carbolic acid or 75% alcohol. You can also roast it over fire.

In the plant growth period, if diseased leaves are found, they should be cut off in time, and the cut waste should be cleaned up, buried deeply, and had better be burned.

To sum up, the diseases we often encounter are as follows.

1. Symptoms and control measures of tillering rot of orchids.

Orchid tiller rot is a bacterial disease. This disease can ruin a year of hard work. It mainly occurs on the tillering bud, initially showing a disease spot the size of mung bean at the base of the bud, and then becomes a dark green scalded patch, extending to the outside of the coleoptile, showing dark brown rot, and the diseased leaves are easy to pull out. The new buds are rotten. Prevention and control methods:

① controls soil water content, and watering of diseased potted flowers should be stopped until the disease is controlled.

When 4mi 5cm was unearthed from ② new buds, 0.01% boric acid solution or 1000 times Dikushuang and Shikujing spraying had a certain effect, and streptomycin could also be used for prevention and treatment.

2. Symptoms and control measures of bacterial brown rot.

Bacterial brown rot is a worldwide disease with wide distribution. China, Japan and the United States are more common. The pathogen is caused by Orchid, which is mainly parasitic in Orchid and Paphiopedilum. In the genus Phalaenopsis, the symptoms are characterized by the appearance of small yellow spots on the leaves, which later become chestnut brown and may sink; they often expand rapidly to the continuous growth of leaves, and then destroy the leaves or even the whole plant. The disease is most common in humid and warm environments. Prevention and treatment: remove the disease part. Then use 200mg/L agricultural streptomycin, or spray 0.5% Bordeaux solution, once every 10 days, with good results.

3. Symptoms and control methods of orchid rot.

The disease mostly occurs in the humid summer rainy season, the common black rot, soft rot and so on. Black rot: caused by Phytophthora. It often occurs in the leaves, roots and growing points, and the disease initially appears translucent spots, then the spots expand, and the tissue blackens and decays. Soft rot: caused by Erwinia and Pseudomonas bacteria. In the early stage of the disease, tiny brown water-immersed spots appear on the leaves, and then expand into gray, moist patches. The epidermis will rupture at the slightest touch, and foul-smelling bacterial pus will flow out. First of all, the disease should keep the plant ventilated and reduce the humidity. At the initial stage of the disease, 50% carbendan 500x solution, 50% bacillus 1000-fold solution, garlic water (mash and soak the garlic in water, take its filtrate) to spray the leaf surface or smear the disease spot. Rotten roots of orchids are easy to induce black spot. Therefore, the pot soil for orchid cultivation should not be too wet at ordinary times. In winter, orchids are in the dormant or slow growth stage, and the basin soil should be dry; spring and early summer are important periods for orchids to take root and draw leaves, and the basin soil should be moist; but if it is too wet for a long time, it is also easy to cause rotten roots and cause leaves to wither and yellow and even die. During the rainy or rainy season, orchids must take shelter from the rain. Because of the long rain and humidity, black spots are most likely to occur on the new leaves, and the stamens of summer orchids often have the phenomenon of "rotten clothes". Affect flowering and ornamental. However, if the basin soil is too dry, it is easy to make the false bulb dry or other tissues affect metabolism due to water loss. Improper fertilization of orchids, such as excessive and concentrated fertilization, and pouring liquid fertilizer into the leaf sheath or splashing on leaves can also easily cause root rot, so fertilization should be applied along the edge of the basin.

4. Symptoms and control methods of orchid root rot.

The pathogen of root rot belongs to Rhizoctonia solanacearum, which mainly lives in the cultivation medium and in the environment of appropriate temperature and humidity, endangers the root tissue of Orchid, resulting in the decrease of the ability of absorbing water and nutrients. There is disharmony between evapotranspiration and absorption, and the orchid plant weakens day by day, which affects the normal growth of the orchid plant. The pathogen of root rot mainly infected the root system, and the injured orchid root had brown disease spot, depression and necrosis in the initial stage. Several severe spots will ring around the base of the stem and new roots or roots will grow, and finally the whole root will rot. In turn, it affects the obstruction and support of water transport, and the harm of root rot pathogens, which can not be detected by the naked eye. Unless the orchid plant is often poured out for observation. By observing the leaves, we found that when the orchid plant grew slowly, the leaf tip scorched, the leaf withered, the bract became black, and then it was too late to find a solution. By this time the root had rotted away. Therefore, we should pay more attention to the acidification of the medium, the permeability, the application of chemical fertilizer, the excessive irrigation of water, the ventilation of the air in the orchid room, the cleanliness of the medium, and the thorough chemical control; the disinfection before planting all affects the growth of orchid plants and causes the root rot. Root rot is a medium-borne disease. Mainly through the adverse environment with dormant hyphae or sclerotia. It occurs most seriously in the old medium with poor wet ventilation, especially in the out-of-date medium, and sometimes the whole root system decays.

Prevention and control methods: (1) usually pay attention to the harm of root mites, root thrips, roundworms and cockroaches. (2) to apply beneficial microbial additives for the prevention and control of bacteria and antibiotics. (3) supplying appropriate amount of phosphate fertilizer and promoting rapid root growth at the initial stage of new bud growth after planting. (4) it is found that the diseased plant should change the medium immediately, and the decaying root system of the orchid plant should be removed before planting. After planting, it should be moved to a cooler place and sprayed with amino acid 2,000 times every three days, so as to avoid insufficient photosynthesis. The nutrients needed to grow new roots are derived from the decomposition of plant cell storage, thus affecting bud germination. (5) do not use irrigation water supply within two days after spraying, but spray water supply instead, keep the medium as dry as possible and accelerate the healing speed.

5. Symptoms and control methods of orchid nematode disease.

The nematode of orchid is a parasitic disease of Orchidaceae. It belongs to the phylum Nematoda, Nematoda, Nematodidae. The adult nematode of orchid is linear and long cylindrical in shape, pointed and thin at both ends, unsegmented, and consists of three germ layers with protoplast cavities. The nematode eggs are very small, the smallest is only 1 micron. The eggs that fall into the plant material absorb water and expand when the plant material is wet, and after the larvae overflow, they invade the root quilt tissue, move upward along the plant to the leaf or mesophyll tissue or the storage tissue of the root to absorb the nutrients of the orchid plant, stimulate the cortical cells and cause the formation of galls. After the adult population of nematodes matured, they mated and laid eggs in the galls. After the eggs in winter hatched into larvae, they stayed in the galls. When the earth returned to spring in the coming year, the larvae would spill out the gall shell, washed by Rain Water and irrigation, fell into the plant substrate, and then re-infected. In the plants with this insect disease, the insect began to migrate to the root integument and leaves of the host in early summer, invading from stomata or water pores, resulting in phosphorus yellow dots on the leaves, and the bottom surface could be seen. After the beginning of autumn, the yellow spot became a thick leathery scab gall, showing a round shape. A fixed-point rough bend appears in the root, and then a flat nodular gall is formed. When the root is degenerated and dried up in winter, the living galls remain in the plant or culture medium. When the spring temperature rises to 18: 22 ℃, the gall larvae overflow and infect other roots and new individuals in the same basin. It happens so repeatedly. For the orchid plants parasitic with nematodes, most of the leaves become thickened and hard, and there are sores and demons, the tillers are abnormal, and most of them can not draw flowering stems.

The prevention and control of orchid nematode disease should give priority to prevention. 1% potassium permanganate solution can be used to rinse the substrate, rinse with clean water, and then use it after drying. When dividing the basin in winter and spring, the leaves with galls should be cut off, and the old roots and roots with galls and dried bracts should be cut off and burned. When it is found that there are round small yellow spots in the leaves, internal absorbent insecticides such as Mudan should be applied immediately; spray 3% on the leaf surface and back. Citric acid absorbs hexazine solution or 800 times rotenone solution, or sprays with 4% Shandao annual water agent; you can also use the above solution to drench the plant material to make the orchid root adsorb.

6. Symptoms and control methods of orchid snow mildew.

The pathogen of orchid snow mildew is a species of Alternaria. Parasitic on Cymbidium and other orchids without pseudobulbs. The symptoms are mainly characterized by the appearance of white powder on the soil, even at the base of the plant stem or extending to other parts. This pathogen is not parasitic on orchids, but lives on cultured soil, consumes nutrients and water, affects air circulation, and thus harms orchids. Therefore, it is necessary to remove the culture soil with bacteria, and mix 40% pentachloronitrobenzene or 50% carbendazim 5~6g/ square meters with fine soil and then mix it into the soil. Plants should also be drenched.

7. Symptoms, prevention and treatment of necrotic ring spot disease in Guolan.

The pathogen is Guolan ringspot virus. The hosts are Caterpillar, Orchid, Magnolia and so on. The symptoms showed that the young and old leaves showed necrotic yellow ring spot or necrotic mottled, the plant was weak and short, and the new and old seedlings may die. Prevention and treatment: the control of virus disease is mainly to remove diseased plants, improve environmental hygiene, disinfect appliances and other methods, in order to prevent its spread. At present, the better disinfectant is: one. 2% formalin and% sodium hydroxide aqueous solution (can no longer be used after turning green); 2. 164g anhydrous or 377g phosphate with crystal water added 1L (1000cc). Can be used for disinfection tools, environment, etc.

8. Symptoms and control methods of orchid wilt.

Orchid wilt disease, also known as Paphiopedilum wilt disease, is widely distributed and is a worldwide disease. The pathogens are Fusarium oxysporum and Fusarium oxysporum: Caterpillar, Orchid, Dendrobium and other orchids. The symptoms of orchid wilt mainly infect the rhizome and make it purple, and the conducting tissue becomes pink-purple, which can also be extended to pseudobulbs and roots. The leaves turned gray due to clogged ducts, and the plants withered and died. Phalaenopsis infected with this disease is often accompanied by root and stem rot. Prevention and treatment: remove diseased plants and soil with bacteria, and spray, soak or irrigate the soil with 50% carbendazim or 50% carbendazim wettable powder 500 times. 0.5% formalin can also be used.

Others such as anthrax, white silk leaf withered and so on have been introduced by orchid friends, and they are no longer wordy this time.

Finally, let's talk about fungicides. When we control diseases, we should use fungicides, which are compounds that can kill pathogenic microorganisms. Fungicides that can kill pathogenic microorganisms play a bactericidal effect, and fungicides that can inhibit the germination or growth of pathogenic spores have bacteriostatic effects, both of which can achieve the purpose of disease prevention and treatment in garden production. There are two ways of action of fungicides: one is protective fungicides, the other is internal absorption fungicides.

Protective fungicides come into direct contact with pathogens in vitro or on the body surface of plants, killing or inhibiting pathogens, making them unable to enter plants, so as to protect plants from pathogens. This kind of fungicide is called protective fungicide, and its function has two aspects: one is to directly kill the pathogen in contact with the pathogen after spraying, that is, "contact germicidal effect"; the other is to spray the fungicide on the surface of the plant, when the pathogenic bacteria are poisoned when they come into contact with the fungicide on the plant, it is called "residual germicidal effect".

Internal absorbent fungicides can be absorbed by crops and transported to other parts of the body after they are applied to a certain part of the body. There are two modes of transmission, one is apical conduction, that is, after the drug is absorbed into the plant, it is transmitted to the apical leaf, terminal bud, leaf and leaf margin along with the transpiration flow to the top of the plant. At present, most of the internal absorption fungicides belong to this category. The other is the basal conduction, that is, the drug is absorbed by the plant and conducts downward along the transport of photosynthetic products in the phloem. There are also some fungicides, such as ethylphosphine aluminum, which can be transmitted up and down.

Fungicides act in different ways and are used in different ways, but fundamentally speaking, there are no more than three principles for fungicides to control diseases, namely, chemical protection, chemotherapy and chemical immunity.

Chemical protection is to spray fungicides before plants get sick to prevent the occurrence of plant diseases. There are only two protective measures for some fungicides: one is to remove the source of infection by spraying at the source of the pathogen, which mainly includes the place where the pathogen overwinters, the intermediate host and the soil and so on. The purpose of eliminating or reducing infection sources through the application of fungicides is to reduce the possibility of pathogens infecting crops. The second is to spray fungicides on the growing crops which are not sick and may be infected by pathogens to prevent the infection of pathogens. After spraying fungicides on the surface of crops, they can kill the pathogenic cells or spores that come to infect the crops. In order to prevent and control the infection of soil-borne pathogens to crops, using fungicides to treat plants before planting belongs to this kind of measures.

After the disease or susceptibility of plants, chemical therapy applies fungicides to protect crops or pathogens, change the pathogenic process of pathogens, and achieve the purpose of reducing or eliminating diseases. Prevention is more important than treatment, and the effect of prevention is also better than that of treatment. Chemotherapy can be divided into three types: one is surface chemotherapy. Some germs, such as powdery mildew, are mainly attached to the surface of plants, which can be killed by stone-sulfur mixture and play a surface therapeutic role. Non-endospermic fungicides can prevent and cure these diseases. One is internal chemotherapy, in which fungicides are introduced into crops to treat germs that have invaded the plant. Only internal inhalation insecticides, such as methyl topiramate and carbendazim, have the effect of internal chemotherapy. The effect of internal treatment of internal inhalation fungicides has two aspects: on the one hand, it is directly toxic to bacteria; on the other hand, it is to change plant metabolism, change its response to bacteria or the pathogenic process of bacteria. However, most internal inhalation fungicides have only one of these effects, and some fungicides have both. One is external chemotherapy, that is, scraping off the plaque after the disease is infected by bacteria, disinfecting the wound with fungicides and coated with protective agents or waterproofing agents to prevent the further expansion of infection.

It is said in the book that penicillin, gentamicin and other things can be effective against orchid black spot, anthrax and white silk disease. Piyanping smear disease spot has a special effect on anthrax. In fact, the pathogenic microorganisms of black spot, anthrax and white silk disease are all fungi, while green, chain and gentamicin "kill" bacteria, and they are only effective against some species of bacteria, not the most effective antibiotics. All kinds of medical textbooks and reference books clearly point out that penicillin is ineffective against fungi. Gentamicin and streptomycin are also ineffective against fungi. Fungi and bacteria are different kinds of microorganisms, have different biological characteristics, and have very different sensitivity to various chemical drugs. The main active ingredient of Piyanping is dexamethasone acetate, which belongs to corticosteroids, which have no inhibitory effect on fungi or bacteria.

When it comes to medication, we have to mention the drug resistance of germs. I used to like to use a special kind of medicine, but I changed it later. Some orchid friends ask if there is a specific medicine. I don't know about this. Maybe there will be in the future. But not now. It is true that long-term use of a drug will lead to drug resistance.

The term "drug resistance" contains two meanings, one is that the genetic material of the pathogen changes and the drug resistance traits can be stably inherited, and the other is that the drug resistant mutants have a certain fitness to the environment, that is, the drug resistant population has the same survival competitiveness as the sensitive population.

The causes of drug resistance of pathogens, diseases and pests.

A single pesticide was used for a long time, and after many times of elimination, a small number of drug-resistant pests and bacteria were preserved, and then continued to multiply to form a resistant population.

Pests with short life history, rapid reproduction, large number and many generations and idiopathic parasitic bacteria are more likely to develop drug resistance. These diseases and insects multiply rapidly, have more exposure to drugs, and develop drug resistance quickly.

Some pests themselves have detoxifying enzymes. When certain pesticides are used for a long time, the activity of detoxifying enzymes is enhanced, which can change the drugs in the body from high toxicity to low toxicity or non-toxicity, and their drug resistance will naturally increase. This is the physiological detoxification of pests, that is, drug resistance in the body.

In addition, under the long-term action of pesticides, some pests are difficult to penetrate the epidermis of insect bodies, thus becoming morphological protection, that is, epidermal drug resistance.

In fungicides, general internal absorption fungicides are easy to cause drug resistance, such as benzimidazole insecticides (carbendazim, topiramate, etc.), antibiotic fungicides and so on. However, contact fungicides are not easy to cause drug resistance, so the best rotation combination. For example, Dyson, inorganic sulfur preparation and copper preparation are better varieties for rotation.

Drug resistance is caused by constant contact, and I have deep feelings about this. In my hometown, there are many orchards, and who pays attention to protective measures when people apply medicine? on a hot day, they run around with the medicine on their bare backs. I felt dizzy when I first came into contact with the medicine, and I got used to it for a long time. When someone came home with medicine, he was hungry and could not wash his hands. He picked up a big bun and ate it, but he was unexpectedly unharmed. (it clears up when it snows fast)