Pesticides refer to the chemical synthesis of one or more substances and their formulations used to prevent, eliminate, or control diseases, insects, grasses, and other harmful organisms that harm agriculture and forestry, as well as to purposefully regulate the growth of plants and insects .
Classified according to mode of action
1. Pesticides
(1) Stomach poison: a drug that enters the insect body through the digestive system and poisons the insect to death. Such as trichlorfon, etc. These pesticides are very effective against pests with chewing mouthparts and licking and sucking mouthparts.
(2) Contact pesticide: through contact with the insect body, the agent enters the insect body through the body wall, causing the insect to be poisoned and killed. Such as most organophosphorus pesticides and pyrethroid pesticides. Contact pesticides can be used to control various mouthpart pests, but they are less effective against scale insects, psyllids, whiteflies, etc. that have waxy secretions on their bodies.
(3) Systemic agents: Agents are easily absorbed by plant tissues, transported within the plant, and transmitted to various parts of the plant, or produce more toxic metabolites through the metabolism of the plant. When pests feed on the plant, they are poisoned and die. Potion. Such as imidacloprid, etc. Systemic agents are particularly effective against pests with piercing-sucking mouthparts.
(4) Fumigants: Agents that can vaporize into toxic gases at room temperature and enter the respiratory system of pests through the spiracles of insects, poisoning and killing the pests. Such as aluminum phosphide, etc. Fumigants should be used under closed conditions for best results. For example, when using aluminum phosphide tablets to control dry borer pests, soil should be used to seal the insect holes.
(5) Specific insect growth regulators: According to their different functions, they can be divided into the following types:
① Insect growth regulator: This agent acts through stomach poisoning or contact killing of insects. Entering the insect body, it hinders the formation of chitin, affects the formation of the inner epidermis, and prevents the insect from molting and metamorphosis. The hatching of eggs and the emergence of adults are blocked or the insect body becomes deformed, thereby exerting the insecticidal effect. This type of agent has high activity, low toxicity, few residues, obvious selectivity, and is safe for humans, livestock and other beneficial organisms. However, the insecticidal effect is slow and the residual effect period is short. Such as Dibenzuron No. 3, Youlede, Taibao, Diflubenzuron, etc.
② Attractant: The agent uses trace amounts of gaseous molecules to lure pests together and annihilate them together. Such agents are further divided into three types: food attractants, sex attractants and spawning attractants. Among them, the most widely used are sex attractants. Such as peach heartworm sex attractant, grape slug moth sex attractant, etc.
③Repellant: acts on the protected object to make the pests unwilling to approach or move or escape, thereby achieving the purpose of protecting crops. Such as mosquito repellent oil, camphor, etc.
④Antifeedant: After being eaten by pests, the agent will destroy the normal physiological functions of the pests, reduce the amount of food taken or stop feeding quickly, and finally cause the pests to starve and die. Such as azadirachtin, antifeedant amines, etc. This type of pesticide itself is not very toxic, but acts on insects with special properties. These agents are generally called specific insecticides.
2. Fungicide
(1) Protective fungicide: Before pathogenic microorganisms invade the host plant, the agent is sprayed on the surface of the plant to form a protective film to hinder the infection of pathogenic microorganisms and protect the plant from harm. Such as Bordeaux mixture, Zinc, Dasheng, etc.
(2) Therapeutic fungicides: When pathogenic microorganisms have invaded the plant, spray pesticides during their incubation period to inhibit their continued expansion in the plant or eliminate their damage. Such as triadimefon, thiophanate-methyl, aluminum ethylphosphonate, etc.
(3) Eradication fungicides: Agents that have a direct and strong killing effect on pathogenic microorganisms. This type of pesticide is often intolerable to plant growth, so it is generally only used for soil treatment before sowing, during plant dormancy or for seedling treatment. Such as lime sulfur mixture, etc.
3. Herbicides
(1) Selective herbicides: This type of herbicide is selective among different plants, that is, it can poison or kill some plants, but is safer for other plants. Most herbicides are selective herbicides. Such as herbicides such as Herbicide and Napropamide all belong to this type of herbicides.
(2) Biocidal herbicides: These herbicides lack or have very little selectivity for plants and can kill most green plants. It kills both weeds and crops, so use with caution. Glyphosate falls into this category of herbicides. It can generally be used to kill weeds on recreational lands, field edges and dam ridges. When used for field weeding, directional spraying is generally used.
