Brief introduction of fungicides
What is a fungicide?
fungicide, also known as biocides, fungicide and algicides, microbicides, etc., usually refer to chemical agents that can effectively control or kill microorganisms in water systems - bacteria, fungi and algae. It is usually a general term for agents used to prevent and control various pathogenic microorganisms.
Background of fungicide production
There are more than 80,000 kinds of pathogenic microorganisms (fungi, strong bacteria, rickettsia, mycoplasma, viruses, algae, etc.) harmful to plants in the world. Plant diseases have caused huge losses to agriculture, and the average annual output of crops in the world has been reduced by about 500Mt. In history, there have been many disasters in which severe famines and even large numbers of people starved to death due to the prevalence of certain plant diseases. The use of fungicides is a cost-effective method of controlling plant diseases.
fungicide, also known as biocides, fungicide and algicides, microbicides, etc., usually refer to chemical agents that can effectively control or kill microorganisms in water systems - bacteria, fungi and algae. Mainly divided into two kinds of agricultural fungicides and industrial fungicides.
Agricultural fungicides
It is a class of pesticides used to prevent and control plant diseases caused by various pathogenic microorganisms, generally referring to fungicides. It is usually a general term for agents used to prevent and control various pathogenic microorganisms. With the development of fungicides, subclasses such as fungicide, virucides, and algicides are distinguished.
Industrial fungicide
According to the bactericidal mechanism, it can be divided into two categories: oxidizing fungicides and non-oxidizing fungicides. Oxidizing fungicides are usually strong oxidizing agents, which mainly achieve the purpose of sterilization through oxidation with metabolic enzymes in bacteria. Commonly used oxidizing fungicides are chlorine, chlorine dioxide, bromine, ozone, hydrogen peroxide, etc. Non-oxidizing fungicides act on special parts of microorganisms in the form of toxic agents, thereby destroying the cells or living organisms of microorganisms to achieve a bactericidal effect. Common non-oxidizing fungicides include chlorophenols, isothiazolinones, and quaternary ammonium salts wait.
Fungicides are classified according to their sources. Except for agricultural antibiotics, which belong to biological source fungicides, the main varieties are chemically synthesized fungicides. Fungicides are a class of agents used to prevent and control plant diseases. All agents that can kill or inhibit the growth of pathogens, but do not hinder the normal growth of plants, are collectively referred to as fungicides. Fungicides can be classified according to their mode of action, source of raw materials, and chemical composition.
Sources of raw materials for fungicides
Inorganic fungicides such as sulfur powder, lime sulfur, copper sulfate, mercury chloride, lime Bordeaux mixture, copper hydroxide, cuprous oxide, etc.
Organosulfur fungicides such as ammonium, thiram, thiram, zinc mancozeb, mancozeb, thiram, etc.
Organophosphorous arsenic fungicides such as Daobenjing, Kewensan, Albium, Tolclofos-methyl, Tuzet, Daojiaoqing, etc.
Substituted benzene fungicides such as thiophanate-methyl, chlorothalonil, dexon, pentachloronitrobenzene, etc.
Azole fungicides such as fenxining, carbendazim, hymexazol, benomyl, thiabendazole, etc.
Antibiotic fungicides Jinggangmycin, polyoxin, kasugamycin, agricultural streptomycin, antimycotic 120, etc.
Compound fungicides such as Mieweiwei, Shuangxiaoling, Anthrax thiram, antivirus alum M8, metalaxyl copper, DT fungicide, metalaxyl manganese zinc, seed dressing manganese zinc, thiophanate-methyl manganese zinc , widely sterilized milk powder, metalaxyl-thiram wettable powder, etc.
Other fungicides such as metalaxyl, sclerotin, procymidone, chlorphenidin, folpet, captan, tefulin, difenazol, Rucucumil, formalin, high lipid film, fungicide Duqing, propamocarb, quicalcetone, dimethomorph mancozeb, etc.
How to use the fungicide
Protective agent
Before the pathogenic microorganisms do not contact the plant or immerse the plant, the plant or the surrounding environment is treated with a medicament to inhibit the germination of the pathogenic spores or kill the germinated pathogenic spores, so as to protect the plant from its harm. This effect is called protection effect. Agents with this effect are protective agents. Such as Bordeaux mixture, zinc zinc, copper sulfate, green milk copper, mancozeb, chlorothalonil and so on.
therapeutic agent
The pathogenic microorganisms of the therapeutic agent have infiltrated the plant, but the plant shows symptoms and is in the incubation period. The drug penetrates into the plant tissue from the epidermis of the plant, and kills or inhibits the pathogen through transduction, diffusion, or production of metabolites, so that the diseased plant will no longer suffer and restore health. Agents that have this therapeutic effect are called therapeutic or chemotherapeutic agents. Such as thiophanate-methyl, carbendazim, kasugamycin and so on.
Eradicants refer to the pathogens that can directly kill the pathogens that have invaded the plants after the plants are infected. Agents with such an eradicating effect are eradicating agents. Such as thiram, sodium pentachlorophenate, lime sulfur and so on.
Biocide Conductivity Properties
Systemic fungicides
Systemic fungicides can be absorbed by plant leaves, stems, roots, and seeds into plants, and can be transported, diffused, retained, or produce metabolites through plant body fluids, which can prevent and control some diseases that penetrate deep into plants or in the endosperm of seeds to protect crops It is not infected by pathogens or treats infected plants, so it has therapeutic and protective effects. Such as carbendazim, polymyxin, frost epidemic clear, thiabactin copper, metalaxyl, phosphonium aluminum, thiophanate-methyl, dikesone, powder rust Ning, nail frost copper, anti-virus alum, seed dressing double and so on.
non-systemic fungicides
Non-systemic fungicides refer to agents that cannot be systemically absorbed by plants, conducted and retained. Most varieties are non-systemic fungicides, which are less likely to cause pathogens to develop resistance and are relatively economical, but most of them only have a protective effect and cannot prevent and control diseases that penetrate deep into the plant. Such as zinc sulfate, copper sulfate, dodine, chlorothalonil, green milk copper, surfactant, synergist, sulfur compound, plant ash, Bordeaux mixture, mancozeb, thiram, chlorothalonil, etc. In addition, fungicides can also be classified according to the method of use, such as seed treatment agents, soil disinfectants, sprays, etc.
protective fungicide
Sulfur and inorganic sulfur compounds, such as sulfur suspending agent, solid lime sulfur mixture, etc.; copper preparations, mainly Bordeaux mixture, copper ammonia mixture, etc.; organic sulfur compounds, such as thiram, zinc, ammonium, mancozeb etc.; phthalimides, such as captan, captan, and foldan; antibiotics, such as Jinggangmycin, blasticidin, polyoxin, etc.; other classes, such as Yekuling, Yekuling Jing, chlorothalonil, Hesui Ning, etc.
How to use the fungicide
There are many ways to use fungicides, and each method of use is designed according to the law of disease occurrence. Common methods of use mainly include: spraying pesticides on field crops, soil disinfection and inoculation disinfection.
For spraying crops in the field, the factors that affect the field disease prevention effect of fungicides are no more than three aspects: pesticides, environment, and crops. However, the application technology of fungicides is more demanding than that of insecticides and herbicides. It is necessary to fully understand the occurrence and development of diseases, because the occurrence and development of diseases are not as clear as insect pests and weed damage.
Two points should be paid attention to when spraying pesticides on field crops: the first is the type and concentration of pesticides. The choice of the type of agent depends on the type of disease, so the correct diagnosis of the type of disease must be made first, and then the right medicine can be prescribed. But it should also be noted that if the same disease occurs on different crops, sometimes the same pesticide cannot be used. For example, Bordeaux mixture can prevent downy mildew, but it is easy to cause phytotoxicity to cabbage, so it is not suitable to control cabbage downy mildew. After the type of medicament is selected, the appropriate application concentration should be selected according to the type and growth period of the crop, the type and dosage form of the fungicide, and environmental conditions.
Ways to improve the effectiveness of fungicides:
Reasonable allocation of concentration
Whether it is a water agent or a wettable powder drug, it needs to be diluted with water before spraying. Different fungicides have different concentration requirements, so the ratio must be strictly followed the instructions, and a reasonable concentration is more conducive to the effectiveness of the fungicide. If the ratio is random, too high concentration will cause phytotoxicity to crops; too low concentration will not meet the control requirements.
Suitable spraying time
The time of spraying fungicides is directly related to the control effect. Spraying too early will cause waste of chemicals and reduce the control effect; too late pathogens have already caused harm to crops. Therefore, it is necessary to use drugs in a timely manner according to the law of occurrence of different diseases, forecasts and specific conditions. Generally speaking, the application time of fungicides can be chosen before or at the beginning of the onset of the disease.
Improve the quality of medication
The application quality of fungicides includes the quantity of application, the frequency of application and the quality of spraying. The amount of medication should be appropriate. Too much medication will increase the cost and cause phytotoxicity, and too little medication will not achieve the control effect. Therefore, increase or decrease according to the specific situation. The frequency of medication depends on the residual effect period of the agent and the weather conditions. Generally, it is sprayed once every 10-15 days, and it is sprayed 2-3 times in total. If it rains after application, respray is required. The method to improve the quality of the medicine is to spray the medicine evenly and finely, and spray it all over the stems and leaves of the plants.
Strictly prevent drug damage
There are many reasons for fungicides to cause phytotoxicity, including the pesticide itself, different sensitivity of crops, growth stage of crops and climatic conditions. Generally speaking, drugs with strong water solubility and crops are more likely to cause phytotoxicity during the seedling stage, booting flowering stage, high temperature and drought, heavy fog and high humidity, so they need to be handled carefully.
Important functions of fungicides
There are two modes of action of fungicides: one is a protective fungicide, and the other is a systemic fungicide. Protective fungicides directly contact the pathogenic bacteria outside or on the surface of the plant, kill or inhibit the pathogenic bacteria, so that they cannot enter the plant, thereby protecting the plant from the harm of the pathogenic bacteria. This type of fungicide is called a protective fungicide, and its function has two aspects: one is to directly kill the pathogenic bacteria after spraying the agent, that is, "contact bactericidal effect"; the other is to spray the agent on the surface of the plant In the past, when the pathogenic bacteria colony on the plant body was poisoned when it came into contact with the agent, it was called "residual bactericidal effect".
Different fungicides work in different ways. The fungicide applied to the surface of the plant before the pathogen infestation has a preventive and protective effect is called a protective fungicide or a protective agent; the fungicide that can eliminate the infected bacteria at the application site is called an eradicating fungicide; Those that are transmitted to the infected part of the body to eliminate the germs are called systemic fungicides. Many eradicating agents are also systemic agents, and most of them have chemical therapeutic effects. Therefore, in practice, fungicides are often simply divided into two modes of action: protective and systemic. Their mechanism of action can also be roughly divided into two categories:
1. Interfere with the respiratory process of germs and inhibit energy production.
2. Interfering with the biosynthesis of bacterial life substances such as proteins, nucleic acids, sterols, etc. Protective fungicides are mostly products with a broad bactericidal spectrum and low bactericidal power. Systemic fungicides generally have strong bactericidal power and narrow bactericidal spectrum, and some varieties have specific selective toxicity to certain pathogenic bacteria. Because the action point of the systemic agent in the bacteria is relatively single, the bacteria are prone to drug resistance due to genetic mutations. In order to avoid or delay the emergence of drug resistance, the appropriate protective agent and systemic agent can usually be selected for mixed application or alternate use, so that better control effects can be obtained by learning from each other. When using, various pesticide application methods such as seed treatment, foliar spraying and soil treatment should be adopted according to the characteristics of the disease occurrence.
Determination method of fungicide
The insecticidal or bactericidal virulence of the agent is often expressed as "lethal median dose", that is, the dose (median lethal dose, mg/kg) required to kill half (50%) of the biological population is often abbreviated as LD50. If the concentration represents the dose, it is the "Lethal Medium Concentration", abbreviated as LC50. Fungicides are expressed by ED50 or EC50, that is, the dose or concentration required to inhibit 50% of spore germination.
Spore Germination Assay
Spray different medicinal liquids on the surface of glass slides or flat plates, quantitatively add spore suspension, and after contacting the medicinal liquids, check the percentage of spore germination under a microscope after a certain incubation time.
Zone of Inhibition
Mix the suspension of pathogenic spores or hyphae with the agar medium, after condensation, place sterilized circular filter paper pieces (about 6 mm in diameter) dipped in different concentrations of medicinal solutions on the surface of the medium, and culture them at a constant temperature for a certain period of time. After a period of time, due to the diffusion of the liquid medicine, the growth of the bacteria is inhibited, that is, an "inhibition zone" is formed. Measure the size of the zone of inhibition to compare the virulence of fungicides.
growth rate assay
Add medicinal solution to the agar medium, inoculate the bacteria after condensation, observe the growth of the colony after 24-48 hours, calculate the growth rate, and compare it with the growth rate of the control group without the medicinal agent.
Precautions for fungicides
Generally, the instruction manual of pesticides has a recommended use concentration, which can be used according to the instructions, but it is better to apply according to the use concentration proposed by the local plant protection technical department based on the efficacy test. In drought or hot summer, the concentration should be reduced to avoid phytotoxicity.
Secondly, when using fungicides, pay attention to the period and frequency of use. The key to mastering the spraying period is to grasp the law of disease occurrence and development, do a good job in the forecasting of disease occurrence, or according to the forecast of crop disease by the local plant protection department Forecast to prepare for spraying fungicides. In general, fungicides are sprayed at the early stage of diseases, such as rice blast, etc. Especially in high temperature weather, rice blast develops rapidly, so they should be sprayed immediately.
The spraying period is determined not only by the law of disease development, but also the growth period of the crops. The occurrence of many diseases is related to a certain growth stage of the crops. In addition, attention should be paid to the tolerance of fungicides in each growth stage of crops to prevent phytotoxicity. The occurrence and development of plant diseases often take a period of time, and it is difficult to solve the problem at one time by spraying fungicides, often requiring multiple sprays. The number of times of spraying mainly depends on the re-infection of pathogens, the residual period of fungicides, and climate conditions, light, temperature and rainfall.
Development prospects of fungicides
Compared with the past, the market speed of pesticide active ingredients has slowed down significantly, among which herbicides have the most obvious decline rate, and insecticides have also declined to a certain extent, while the market introduction of new fungicides has been very strong.
There are a total of 17 new pesticide varieties disclosed globally, and fungicides account for 9, more than 50%, of which 3 are amide compounds, 3 are methoxyacrylate compounds, 1 triazolopyrimidine compound, 1 quinoline compounds, and another antiviral agent, fluorophos.
Reasons for good prospects of global fungicide production and application
1. The degree of agricultural intensification has been continuously strengthened;
2. It is the frequent occurrence of extreme weather that drives the demand of the fungicide market;
3. The demand for fungicides in non-pesticide fields continues to increase rapidly and the profit margin is large;
4. Some high-efficiency fungicide patents will expire during the "Twelfth Five-Year Plan" period;
5. During the "Twelfth Five-Year Plan" period, the state will continue to encourage scientific and technological innovation, and fungicide varieties with independent intellectual property rights will continue to be developed and put into the market;
6. The ever-expanding planting area of genetically modified crops will have a great negative impact on pesticides and herbicides, but will have little impact on fungicides
The price of fungicides
Usually, the price of pesticides and fungicides will be affected by raw materials, market environment, research and development costs, etc. If you want to know the latest price of the pesticide fungicide you need, please contact us to initiate an inquiry.
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