What Is a Microbicide?

Fungicides are also known as biocides, bactericidal algicides, microbicides, etc., and generally refer to chemical agents that can effectively control or kill microorganisms in the water system-bacteria, fungi and algae. In the international arena, it is generally used as a generic term for agents used to control various types of pathogenic microorganisms.

Fungicides are also known as biocides, bactericidal algicides, microbicides, etc., and generally refer to chemical agents that can effectively control or kill microorganisms in the water system-bacteria, fungi and algae. In the international arena, it is generally used as a generic term for agents used to control various types of pathogenic microorganisms.

Chinese name

Fungicide

Foreign name

Industrial Bactericide

Pinyin

sha jun ji

Definition

Agents for controlling various pathogenic microorganisms

Classification

Bactericide, virus killer, algicide

Opening event

Using organic mercury compounds to control wheat smut

Ingredients

Inorganic compounds

Mode of action

Protective fungicide

Background of fungicides

According to surveys, there are more than 80,000 species of pathogenic microorganisms (fungi, strong bacteria, rickettsia, mycoplasma, viruses, algae, etc.) harmful to plants worldwide. Plant diseases have caused huge losses to agriculture, and crops around the world have reduced their average annual yield by about 500 Mt. There have been many times in the history of severe famine caused by the epidemic of certain plant diseases, and even a large number of people starved to death. The use of fungicides is a cost-effective method for controlling plant diseases.

Main types of fungicides

Fungicides are also known as biocides, bactericidal algicides, microbicides, etc., and generally refer to chemical agents that can effectively control or kill microorganisms in the water system-bacteria, fungi and algae. It is mainly divided into agricultural fungicides and industrial fungicides.

Agricultural fungicide

It is a type of pesticide used to control plant diseases caused by various pathogenic microorganisms, and generally refers to fungicides. However, internationally, it is generally used as a generic term for agents that control various types of pathogenic microorganisms. With the development of fungicides, bactericides, virus killers, algicides and other subclasses are distinguished.

Industrial fungicides

Oxidative sterilization

Fungicide

Agents and non-oxidizing fungicides. Oxidizing bactericides are usually strong oxidants, and they achieve sterilization mainly by oxidizing with metabolic enzymes in bacteria. Commonly used oxidizing fungicides are chlorine, chlorine dioxide, bromine, ozone, hydrogen peroxide, and the like. Non-oxidizing fungicides are toxic agents that act on special parts of microorganisms, thereby destroying the cells or living organisms of microorganisms and achieving sterilizing effects. Common non-oxidizing fungicides include chlorophenols, isothiazolinones, and quaternary ammonium salts. Wait.

Fungicides are classified according to their source. Except for agricultural antibiotics, which are biologically-derived fungicides, the main species are chemical synthetic fungicides. Fungicides are a class of agents used to control plant diseases. Any agent that has a killing effect on the pathogen or inhibits growth but does not hinder the normal growth of the plant is collectively referred to as a fungicide. Fungicides can be classified according to their mode of action, source of raw materials, and chemical composition.

Fungicides by application area

Divided into two kinds of industrial fungicides and agricultural fungicides according to the application field.

Fungicides are divided according to the raw material source of the fungicide

Biocide

Such as sulfur powder,

Fungicide

Stone sulfur mixture, copper sulfate, mercury, lime Bordeaux solution, copper hydroxide, cuprous oxide, etc.

Organic sulfur fungicide

Such as ammonium, sodium dirust, fumezine, zirconium, mancozeb, fumezine and so on.

Organophosphorus and arsenic fungicides

Such as rice blast net, gram blast powder, ethidium aluminum, methyl cumulant, bacteriostatic, rice foot green and so on.

Fungicides replace benzene fungicides

Such as methyl tolbutin, chlorothalonil, dicotrim, pentachloronitrobenzene and so on.

Azole fungicides

Such as Fenru Ning, Carbendazim, Moxacillus, Benconazole, Thicarbin and so on.

Fungicides

Jinggangmycin, polyoxin, kasugamycin, agricultural streptomycin, antimycin 120, etc.

Fungicide

Such as Feiweiwei, Shuangxiaoling, Anthracnose Fume, Antiviral Alum M8, Metalaxyl Copper, DT Fungicide, Metalaxyl · Manganese-Zinc, Seed Dressing · Manganese-Zinc, Methylthiobendazim · Manganese-Zinc, Widely Sterilized Milk powder, metalaxyl-Fumei Shuang wettable powder.

Other fungicides

Such as metalaxyl, sclerotinia, humilis, hydrazone, sterilized dan, kelendazol, tefulin, dicarbendazim, rhizopus, formalin, high lipid film, bacteriotoxin, Propadicarb, quinacridone, dimethomorph · manganese zinc, etc.

Fungicides are classified according to how they are used

Fungicide protective agent

Protective agent: Before the pathogenic microorganisms do not come into contact with the plant or immerse them in the plant body, treat the plant or the surrounding environment with the agent to achieve the inhibition of the germination of the pathogenic spores or the killing of the germinated pathogenic spores in order to protect the plant from its damage. effect. An agent having such an effect is a protective agent. Such as Bordeaux solution, zinc substitute, copper sulfate, green milk copper, zinc substitute manganese, chlorothalonil and so on.

Fungicides

The therapeutic agent pathogenic microorganism has been immersed in the plant, but the plant manifests a disease in a latent period. The drug infiltrates from the plant epidermis into the inside of the plant tissue, and is killed or inhibited by the transmission, diffusion, or production of metabolites, so that the diseased plant is no longer harmed and the health is restored. An agent having such a therapeutic effect is called a therapeutic agent or a chemotherapeutic agent. Such as methyl tolbutin, carbendazim, kasugamycin and so on.

3. Eradication agent refers to the application of pesticides that can directly kill pathogens that have invaded plants. An agent having such an eradication action is an eradication agent. Such as Fumei arsenic, sodium pentachlorophenol, stone sulfur mixture and so on.

Fungicides are classified by conduction characteristics

Systemic fungicide

Systemic fungicides can be absorbed into plant bodies by plant leaves, stems, roots, and seeds, and can be transmitted, diffused, retained, or metabolized by plant body fluids, which can prevent some diseases that penetrate into the plant or within the endosperm of the seed to protect the crop. It is not affected by pathogens or treats infected plants, so it has a therapeutic and protective effect. Such as Carbendazim, Lectobacillus, Lvheng No. 2, Carbendazim, Phytophthoracin, Thiobacillus, Metalaxyl, Ethylphosphine, Methyltobutzine, Dixon, Fenoxin, Metalaxyl Copper, and Antiviral Alum , Double seed dressing.

Non-systemic fungicide

Non-systemic fungicide means that the agent cannot be systemically absorbed, conducted and retained by the plant. Most varieties are non-systemic fungicides. Such agents are not easy to cause resistance to pathogens and are relatively economical, but most of them only have a protective effect and cannot prevent diseases that penetrate into the plant. Such as zinc sulfate, copper sulfate, dodine, chlorothalonil, green milk copper, surfactants, synergists, sulfur mixtures, plant ash, Bordeaux solution, mancozeb, fomesal, chlorothalonil and so on. In addition, fungicides can be classified according to the use method, such as seed treatment agents, soil disinfectants, spraying agents and so on.

Protective fungicide

There are mainly the following categories: sulfur and inorganic sulfur compounds, such as sulfur suspending agents, solid stone sulfur mixtures, etc .; copper preparations, mainly Bordeaux liquid, copper ammonia mixture, etc .; organic sulfur compounds, such as Fumei Shuang, Daisen Zinc, Daisen Ammonium, mancozeb, etc .; ammonium phthalimide, such as ketotan, dichlorvan, and sterilant, etc .; antibiotics, such as Jinggangmycin, blasticidin, polyoxin, etc .; other classes, such as Ye Kuling, Ye Kujing, chlorothalonil, Hesui Ning, etc.

History of fungicides

Early bactericides were inorganic compounds, such as sulfur powder and copper preparations (see Bordeaux Solution), which are still used today. In 1914, I. Riem of Germany first used organic mercury compounds to control wheat smut, marking the beginning of the development of organic fungicides.

In 1934, WH Tisdale and others in the United States discovered the bactericidal properties of dimethyldithiocarbamate, after which organic fungicides began to develop rapidly. In the 1950s and 1950s, there were three main series of organic sulfur fungicides: Fome, Daisen (such as Daisen Zinc), and trichloromethylthiodimethylcarboximide. In addition, organic chlorine, organic mercury, Organic arsenic fungicides have also been developed. Most of these fungicides are protective agents and have limitations in application.

Since the 1960s, more chemical types of fungicides have continuously appeared, the most important of which is the advent of systemic fungicides.

In 1965, Japan developed the organophosphate fungicide rice blast net, in 1966 the United States developed rust-proof spirit, in the United States in 1967, Benzendazol, in Japan in 1969, Thiopenthrin, in 1974, the Federal Republic of Germany, azoxystrobin, and Tricyclazole was developed in the United States, metalaxyl in Switzerland in 1977, and aluminum triethyl phosphate in France in 1978. The systemic agent represented by the above has become the mainstream of fungicide development since the 1970s. At the same time, agricultural antibiotics have also developed rapidly. Organic mercury, organic arsenic, and some organochlorine fungicides are being phased out due to toxicity or environmental pollution issues. The new generation of systemic agents has further expanded the market for bactericides due to improved control effects. By the 1980s, there were more than 200 species of fungicides. According to surveys, worldwide sales of fungicides reached US $ 2.54 billion in 1985, accounting for 18.4% of total pesticide sales.

In 1984, sales of systemic agents in fungicides accounted for 44.2%, and non-systemic agents accounted for 55.8%. For nearly half a century, the development of fungicides has mainly focused on the prevention and treatment of fungal diseases, while the research and development of the prevention and treatment of bacterial and virus-induced diseases has been insufficient. China has mainly developed protective fungicides since the 1950s. Since the 1970s, it has started to develop systemic fungicides and agricultural antibiotics, and stopped using organic mercury agents. Because the application technology of fungicides is relatively complicated, the development speed is not as fast as pesticides, but the role of fungicides in increasing agricultural production has been increasingly recognized by farmers. With the modernization of Chinese agriculture, the development of fungicides will surely accelerate. Instructions

Fungicide operation method

There are many ways to use fungicides, and each use method is designed according to the law of disease occurrence. The common use methods are: spraying on the ground crops in the field, disinfecting the soil and disinfecting the bacteria.

For field crop spraying, the factors that affect the field disease prevention effect of fungicides are nothing more than three aspects of pesticides, environment, and crops, but the application technology of fungicides is more demanding than that of pesticides and herbicides, especially It is necessary to fully understand the occurrence and development of diseases, because the occurrence and development of diseases are not as clear as insects and grasses.

Pay attention to two points when spraying field crops: first is the type and concentration of the pesticide. The choice of the type of medicine depends on the type of disease, so a correct diagnosis of the disease type must be made before the right medicine can be prescribed. For example, rice blast can be selected from rice blast net, rice blast spirit, tricyclazole, etc .; wheat powdery mildew, rust should be selected from triazolol, triazolone, etc .; However, it should also be noted that if the same disease occurs on different crops, sometimes the same agent cannot be used. For example, Bordeaux solution can prevent downy mildew, but it is easy to cause damage to cabbage, so it is not suitable to control downy mildew of cabbage. After selecting the type of agent, the appropriate application concentration should be selected according to the type of crop and growth period, the type and formulation of fungicide, and environmental conditions.

Methods to improve the effect of fungicides:

Reasonable concentration

Regardless of whether it is a water or wettable powder drug, it needs to be diluted with water before spraying. Different concentrations of bactericides are required, so the ratios must be strictly followed according to the instructions. A reasonable concentration is more conducive to the effectiveness of the bactericides. If the ratio is arbitrarily, too high a concentration will cause phytotoxicity to the crops; too low a concentration will not meet the control requirements.

Suitable spraying time

The time of spraying the fungicide has a direct relationship with the control effect. Premature spraying will cause waste of the drug and reduce the control effect; too late the pathogen has caused harm to the crop. Therefore, it is necessary to take medicines in a timely manner according to the occurrence of different diseases, predictions and specific conditions. In general, the time of administration of the bactericide can be selected before or at the beginning of the onset.

Improve medication quality

The quality of bactericides used includes the number of drugs used, the number of times used and the quality of sprays. The amount of medicine should be appropriate. Too much medicine will increase the cost and cause harm, and too little medicine will not achieve the effect of prevention and control. Therefore, increase or decrease according to the specific situation. The number of doses can be determined by the residual period of the agent and the weather conditions. Generally, it is sprayed every 10-15 days for a total of 2-3 sprays. In case of rain after application, make up spray. The method of improving the quality of the medicine is to spray the fog point evenly and finely, spraying the stems and leaves of the plants.

Prevent phytotoxicity

There are many reasons for bactericidal damage caused by fungicides, which are affected by the medicament itself, different crop sensitivities, crop growth stages and climatic conditions. In general, medicines and crops with higher water solubility have a greater chance of causing harm in the seedling stage and booting flowering stage, high temperature and drought, fog weight and high humidity, and so need to be handled with caution. ^[1]

Important fungicide functions

New Jieer

There are two modes of action of germicides: one is a protective germicide, and the other is a systemic germicide. Protective fungicides come into direct contact with pathogenic bacteria outside or on the surface of the plant, killing or inhibiting the pathogenic bacteria and preventing them from entering the plant, thereby protecting the plant from the harm of pathogenic bacteria. Such fungicides are called protective fungicides, and their effects have two aspects: one is to directly contact the pathogenic bacteria after spraying the agent to kill the pathogenic bacteria, which is "contact bactericidal effect"; the other is to spray the agent on the surface of the plant In the above, when the pathogenic colonies come into contact with the agent on the plant body and are poisoned, it is called "residual bactericidal effect".

Different fungicides work differently. Protective fungicides that are applied to the surface of a plant before they infect them are called protective fungicides, that is, protective agents; those that can destroy infected bacteria at the application site are called eradicative fungicides; they can be absorbed by plants and can Systemic bacteria are known as systemic fungicides, which are transmitted to the site where the germs infect. Therefore, in practice, fungicides are often simply divided into protective and systemic action modes. Their mechanism of action can also be roughly divided into two categories:

1. Interfering with the respiratory process of germs and inhibiting the production of energy.

2. Interfering with the biosynthesis of bacterial organisms such as proteins, nucleic acids, and sterols. Protective fungicides are mostly products with a broad bactericidal spectrum and low bactericidal power. Systemic fungicides generally have a strong bactericidal power and a narrow bactericidal spectrum. Some of these species have specific selective toxicity to certain pathogens. Because the systemic point of action of the systemic agent in the bacteria is relatively single, pathogens are susceptible to resistance due to mutations in genetic genes. In order to avoid or delay the development of drug resistance, an appropriate protective agent and a systemic agent can usually be selected for mixed application or rotation. This can be used to complement each other to obtain better control effects. According to the characteristics of disease occurrence, various application methods such as seed treatment, foliar spraying and soil treatment should be adopted during use.

Fungicide Industrial Application

Application of biocides in industrial circulating cooling water

1. Quaternary ammonium fungicides: dodecyldimethylbenzyl ammonium chloride, dodecyldimethylbenzylammonium bromide, tetradecyldimethylbenzylammonium chloride, polyquater Ammonium salts, etc.

2. Chlorine-containing bactericides: chlorine gas, chlorine dioxide, sodium dichloroisocyanurate (Ultrachloride), sodium trichloroisocyanurate, etc.

3. Peroxide fungicides: hydrogen peroxide, peroxyacetic acid, etc.

4, oxazoline: isothiazolinone, benzoisothiazolinone, etc.

5. Aldehydes: glutaraldehyde, etc.

Application of Fungicide in Waterborne Coating Industry

Oxazoline: isothiazolinone, benzoisothiazolinone, etc.

Fungicide precautions

General pesticide instruction manuals have recommended concentrations,

It can be used according to the instructions, but it is best to apply it according to the concentration used by the local plant protection technical department based on the efficacy test. Dry or hot summer should reduce the use concentration to avoid drug damage. Secondly, when using fungicides, pay attention to the use period and the number of uses. The key to mastering the spraying period is to grasp the law of disease occurrence and development, do a good job of forecasting the occurrence of disease, or according to the forecast of crop diseases by the local plant protection department. Forecast to prepare for spraying fungicides. In general, the spraying of fungicides is carried out at the early stage of the disease, such as rice blast. Especially in high temperature weather, rice blast develops quickly and should be sprayed immediately. However, the development of peanut leaf spot disease is relatively slow. Do not spray easily when the disease just starts, let alone spray before the disease, but start spraying when a certain development trend is formed after the disease. Climatic conditions are conducive to spraying medicine when the disease develops rapidly. Sometimes, in order to control the disease, it is necessary to spray medicine at drizzle. The spraying period is determined by the development of the disease, and the growth period of the crop must be considered. Many diseases are related to a certain growth stage of the crop. In addition, we must pay attention to the tolerance of the crops to the fungicides during each growth period to prevent the occurrence of pesticide damage. The occurrence and development of plant diseases often take a period of time, and spraying fungicides is also difficult to solve the problem at one time, often spraying multiple times. The number of sprays is mainly determined by the re-infection of the bacteria, the residual period of the fungicide, and the climatic conditions, light, temperature and rainfall. Seedling disinfection. Emulsions and solutions should be used for soaking seeds, not suspensions, that is, wet powders should not be used for soaking seeds. The key to seed soaking is the concentration of the chemical solution and the time of soaking. Improper operation will cause poor sterilization effect or cause harm to the medicine. Other factors such as temperature, seed type, and location of the germs also affect the effect of seed soaking. In general, after the seed type, air temperature, and the type of agent are determined, the concentration of the agent and the soaking time can be coordinated, and the high concentration can appropriately extend the soaking time. The deeper part of the germ or the hard seed coat can appropriately extend the soaking time, and the high temperature can appropriately shorten the soaking time. Seed dressing requires that both the seed and the medicinal powder must be dry, otherwise it will cause uneven seed dressing, cause medicinal damage, and affect the germination rate of the seed. The amount of medicinal powder generally accounts for 0.2% to 0.5% of the weight of the seed. When dressing the seed, the medicament and seeds must be added in 3 to 4 batches, and then the seed dressing container is appropriately rotated to mix it evenly. After the emergence of systemic fungicides, a new seed dressing method, wet dressing method, appeared. That is, the powder is wet with a small amount of water, and then the seeds are mixed, or the dry powder is mixed with the wet seeds to make the powder adhere to the surface of the seeds. After the seed is sown, the powder slowly dissolves and is absorbed into the plant body for upward conduction. Soil-borne diseases such as cotton fusarium wilt and cucumber fusarium wilt can be controlled by soaking or mixing seeds, as well as by soil disinfection. Soil disinfection must first select an appropriate fungicide according to the type of disease, and then select an appropriate soil treatment method based on the physicochemical properties of the agent and the soil structure and properties. The watering method is suitable for water-soluble fungicides. After adjusting the drug to an appropriate concentration, watering a solution of about 5 to 10 kg per square meter of ground. When the soil is dry, a lower concentration of the liquid can be used, and the irrigation volume can be appropriately increased. ; When the soil is wet, high-concentration and small-volume irrigation can be used. Bactericides with higher vapor pressure can be applied by plow bottom or furrow, that is, the powder or liquid is evenly spread on the bottom of the first plough, and the soil is covered with the soil turned over by the second plough. This method is not suitable for too much. For sticky soil, you can also apply medicine powder or liquid to the surface of the soil, and then turn the soil to bury the medicine into the soil.

Fungicide determination method

The insecticidal or bactericidal virulence of pharmaceuticals is often expressed as "lethal medium dose", that is, the median lethal dose (mg / kg) required to kill half (50%) of the biological population is often abbreviated as LD50. If the concentration represents a dose, it is the "lethal concentration", abbreviated as LC50. Bactericide is expressed by ED50 or EC50, which is the dose or concentration required to inhibit 50% of spore germination.

Fungicide spore germination assay

Spray different chemical solutions on the surface of a glass slide or a plate, and quantify the spore suspension dropwise. After contacting the chemical solution, after a certain incubation time, inspect the percentage of spore germination under a microscope.

Bacteriostatic zone

Mix the suspension of pathogenic spores or hyphae with the agar medium. After condensing, place a circular filter paper (about 6 mm in diameter) sterilized and dipped in different concentrations of the drug solution on the surface of the medium. After a period of time, due to the diffusion effect of the medicinal solution, the growth of germs is inhibited, that is, an "inhibition circle" is formed. The size of the inhibition circle is measured to compare the virulence of the fungicide.

Biocide growth rate assay

In the method of adding a chemical solution to the agar medium and condensing the bacteria, after 24 to 48 hours, observe the growth of the colonies, calculate the growth rate, and compare the growth rate with the control group without the agent.

Development prospects of fungicides

The market speed of pesticide active ingredients is now significantly slower than in the past. Among them, the rate of herbicide decline is the most obvious, and pesticides have also declined to a certain extent. However, the market introduction of new fungicide products has been very strong, especially in recent years.

In 2009, there were a total of 17 new pesticides published worldwide, and 9 fungicides accounted for more than 50%. Among them, 3 were amide compounds, 3 were strobilurin compounds, and 1 was triazolopyrimidine. Compound, a quinoline compound, and an antiviral agent, fluorophosphine. During the "Eleventh Five-Year Plan" period, a total of 34 domestic pesticides with independent intellectual property rights obtained pesticide registration licenses, of which 17 were fungicides, occupying half of the country. The main varieties are flumorph, oxystrobin, pyracoxazole, Enoxime, aureus, etc.

Reasons for Good Global Bactericide Production and Application Prospects

1. The degree of agricultural intensification has been continuously strengthened;

2. Frequent extreme weather has stimulated the demand of the fungicide market;

3. The demand for bactericides in the non-pesticide field continues to increase rapidly and the profit margin is large;

4. Some patents of high-efficiency fungicide varieties will expire during the "12th Five-Year Plan" period;

5. During the "Twelfth Five-Year Plan" period, the state will continue to increase technological innovation, and fungicide varieties with independent intellectual property rights will continue to be developed and put on the market;

6. The growing area of genetically modified crops will have a great negative impact on pesticides and herbicides, but will have little effect on fungicides.