The meaning and classification of pesticides

(1) The meaning of pesticides

Pesticides are short for agricultural chemicals. According to the "Pesticide Management Regulations" promulgated by the State Council on May 8, 1997, China's definition of pesticides is: pesticides are used to prevent, eliminate or control diseases, insects, grasses and other harmful organisms that are harmful to agriculture and forestry, and have a purpose. A chemical synthesis of plants, insect growth, or a mixture of one or more substances derived from organisms, other natural substances, and preparations thereof.

(2) Classification of pesticides

There are many classification methods for pesticides, which can be classified according to the source, the target of control, and the mode of action of pesticides.

1. Classification by function mode

(1) Insecticides

1 Stomach poisoning agent that enters the worm through the digestive system and causes the poisoning of the pest. Such as trichlorfon and so on. These pesticides are very effective against pests of chewing mouthpieces and sucking mouthparts.

2 Touching agent An agent that enters the body of the insect through the body wall and causes the pest to die by contact with the pest. Such as most organophosphate insecticides, pyrethroid insecticides. The contact agent can be used to control pests of various mouthparts, but the effect of the scale insects such as scale insects, hibiscus, whitefly and the like is poor.

3 Systemic agents Drugs are easily absorbed by plant tissues and transported in plants, transmitted to various parts of the plant, or metabolized by plants to produce more toxic metabolites, poisoning and death agents when the pests feed on plants. Such as dimethoate, imidacloprid and so on. The systemic agent is particularly effective against pests of sucking mouthparts.

4 Fumigant A chemical that can be vaporized into a toxic gas at room temperature, enters the respiratory system of the pest through the valve of the insect, and causes the poisoning of the pest. Such as aluminum phosphide. The fumigant should be used under closed conditions. If the aluminum phosphide tablet is used to control the pests, the wormholes are sealed with soil.

5 Specific insect growth regulators can be divided into the following types according to their functions:

1) Insect growth regulators. The agent enters the insect body through insect stomach poisoning or contact killing, hinders the formation of chitin, affects the formation of the inner epidermis, and prevents the insect molting from going smoothly. The hatching of the egg and the emergence of the adult are hindered or the body becomes deformed. Play the insecticidal effect. These agents have high activity, low toxicity, low residue, obvious selectivity, and are safe for humans, animals and other beneficial organisms. However, the insecticidal effect is slow and the residual effect period is short. Such as chlorfenapyr No. 3, Youle, Yitaibao, diflubenzuron, etc.

2) Attractant. The agent seduce the pests with a trace amount of gaseous molecules to annihilate several kinds of annihilation. These agents are further divided into three types: food attractants, sexual attractants, and oviposition attractants. Among them, sex attractants are widely used. Such as peach small heartworm attractant, grape winged moth sex attractant.

3) Repellent. It acts on the protected object, making the pests unwilling to approach or transfer, escaping the imagination and achieving the purpose of protecting the crop. Such as mosquito repellent oil, camphor and so on.

4) Antifeedant. After the pesticide is taken by the pest, the normal physiological function of the pest is broken, the feeding amount is reduced or the feeding is quickly stopped, and finally the pest is starved and died. Such as azadirachtin, anti-ecohol and so on.

These insecticides are not very toxic by themselves, but act on insects with special properties. These agents are generally referred to as specific insecticides.

In fact, the insecticidal action of insecticides is not entirely singular, and most insecticides often have several insecticidal modes. For example, dichlorvos has three modes of action: contact, stomach poisoning and fumigation, but it is mainly based on contact. When choosing to use pesticides, you should pay attention to the main insecticidal action.

(2) fungicides.

1 Protective fungicide. Before the pathogenic microorganism has invaded the host plant, the agent is sprayed on the surface of the plant to form a protective film, which hinders the infection of the pathogenic microorganism, thereby protecting the plant from the harmful agent. Such as Bordeaux liquid, Daisen zinc, Dasheng and so on.

2 therapeutic fungicides. The pathogenic microorganism has invaded the plant and sprayed the agent during its incubation to inhibit its continued expansion or destruction in the plant. Such as triazolone, thiophanate-methyl, ethyl aluminum phosphate and the like.

3 eradication fungicides. An agent that has a direct and strong killing effect on pathogenic microorganisms. Such agents are often unbearable for plant growth, so they are generally only used for soil treatment before sowing, and for seedlings during plant dormancy. Such as stone sulfur mixture, Fumei 胂 and so on.

(3) Herbicides .

Selective herbicides. Such herbicides are selective among different plants, ie are capable of poisoning or killing certain plants, while being safer for others. Most herbicides are selective herbicides. Such as herbicide, dichlorfen, etc. are all such herbicides.

Killer herbicide. These herbicides are not selective for plants, or have little selectivity and can kill most green plants. It kills both weeds and crops, so be careful when using them. Paraquat and glyphosate are such herbicides. Generally used for leisure, land and dams to kill grass. Directional spray is generally used for pastoral weeding.

2. According to the classification of control objects, it can be divided into insecticides, acaricides, fungicides, nematicides, herbicides, rodenticides and plant growth regulators.

(1) Insecticides. An agent for controlling pests. Such as imidacloprid, dichlorvos and the like.

(2) Acaricide. An agent for controlling pests. There are specific acaricides (such as Nisolang, Kruth, etc.) and insecticidal acaricides (such as fenpropathrin, anthrone, etc.).

(3) fungicides. An agent for controlling phytopathogenic microorganisms. Such as Bordeaux mixture, chlorothalonil and so on.

(4) Herbicides. An agent used to control weeds in garden fields. Such as dichlorfen, propisochlor, paraquat and so on.

(5) nematicides. An agent for controlling phytopathogenic nematodes. Such as Weibaimu and so on.

(6) Rodenticide. An agent for controlling rodents. Such as the enemy sodium salt, fluconne and so on.

(7) Plant growth regulators. An agent for promoting or inhibiting the growth and development of a plant. Such as gibberellin, ethephon and so on.

3. Classification of pesticide sources According to the source, pesticides can be divided into three categories: mineral source pesticides, biological source pesticides and chemical synthetic pesticides.

(1) Mineral source pesticides. Mineral-derived pesticides are processed from mineral raw materials such as stone sulphur mixture, Bordeaux mixture, king copper (basic copper chloride), and oil emulsion.

(2) Biological source pesticides. Pesticides developed from natural biological resources (such as plants, animals, and microorganisms) when they are biologically derived. Due to different sources, it can be divided into plant-derived pesticides, animal-derived pesticides and microbial pesticides.

1 Plant-derived pesticides. Plant-derived pesticides are processed by natural plants, such as pyrethrin, nicotine, rotenone, glycosides, brassinolides, and the like. Such pesticides are generally less toxic, safe to humans and animals, and free from phytotoxicity to plants, and pests are not susceptible to drug resistance.

Botanical pesticides also include plant pesticides. It mainly refers to genetically modified pest-resistant or herbicide-tolerant crops, such as insect-resistant cotton that has been widely used in China. With the continuous development of biotechnology, GM plants that are resistant to pests and weeds will be widely used.

2 Animal source pesticides. Animal-derived pesticides are mainly divided into three categories: one is the toxin produced by animals, and they are toxic to pests. The silkworm toxin produced by marine animal silkworm is the most typical animal toxin and has become a major type of insecticide. The second is hormones produced by insects, including brain hormones, juvenile hormones, ecdysone and the like. They have the function of regulating the growth and development of insects. Insect pheromones, also known as insect pheromones, have the functions of attracting, stimulating, inhibiting, controlling insect feeding or mating and spawning. The third is animal pesticides, which refers to commercial natural enemy insects, predatory mites and insects modified by physical or biotechnology. China has made progress in the research and application of various natural enemies such as Trichogramma, Scorpion bee, and Lily wasp.

3 microbial pesticides. Microbial pesticides include agricultural antibiotics and living microorganisms. Agricultural antibiotics are metabolites produced by fermentation of antibiotics and have pesticide functions. Such as polymycin, liuyangmycin, avermectin and so on. In vivo microbial pesticides are pathogenic microorganisms of harmful organisms. Such as Beauveria bassiana, Bacillus thuringiensis, nuclear polyhedrosis virus, Lu Bao 1 and so on. Microbial pesticides generally have no phytotoxicity to plants, have little impact on the environment, and are not susceptible to resistance by harmful organisms.

As the demand for pollution-free food, green food, and organic food continues to increase, the types and demand for biological pesticides will continue to grow.

(3) Chemically synthesized pesticides. Synthetic pesticides are artificially developed when chemically synthesizing pesticides. The chemical structure of synthetic pesticides is very complicated, with many varieties, many varieties, large production capacity and wide application range. It has become the most used class of pesticides today. At present, most of the pesticides used in the production of horticulture, fruit trees and flowers belong to this category. It is necessary to add more new varieties of pesticides suitable for the production needs of “no pollution products” and “green foods”, improve quality, and more effectively eliminate diseases, insects, grasses and other pests.