Most insecticides have several ways of killing insects. For example, dichlorvos has three action modes: touch killing, stomach poisoning and fumigation, but the main action mode is touch killing. When selecting and using pesticides, attention should be paid to the selection of their main insecticidal methods in order to use fewer drugs and more insecticides.
The selectivity of herbicides to plants is very low. They can kill weeds as well as crops. They should be used with great caution. Paraquat and glyphosate belong to this kind of herbicide.
Pesticides are short for agricultural medicines. According to the Regulations on Pesticide Management promulgated by the State Council on May 8, 1997, pesticides in China are defined as pesticides, which are used to prevent, eliminate or control diseases, insects, grasses and other harmful organisms harmful to agriculture and forestry, as well as chemical synthesis that purposefully regulates the growth of plants and insects, or are derived from organisms and other natural resources. A mixture of one or more substances and their preparations.
Pesticides are classified according to their mode of action
(1) Gastric poison enters the insect body through the digestive system, causing the insect to poison and die. Such as the enemy. These pesticides are very effective against pests of chewing mouthparts and sucking mouthparts.
(2) Contact killer is a kind of drug that can poison and kill insects by contacting with the insect body and entering the insect body through the body wall. For example, most organophosphorus insecticides and pyrethroid insecticides. Contact killers can be used to control various mouth organ pests, but they have poor effects on scale insects, psylla, whitefly and so on.
(3) Internal absorbent agents are easily absorbed by plant tissues and transported to various parts of plants, or produce more toxic metabolites through plant metabolism. When pests feed on plants, they are poisoned and killed. Such as imidacloprid and so on. Inspirators are especially effective against insects of puncture-suction mouthparts.
(4) Fumigant agents can be gasified into toxic gases at room temperature, and enter the respiratory system of pests through the valve of insects, so as to poison and kill pests. Such as aluminum phosphide and so on. Fumigants should be used under closed conditions to achieve good results. If aluminium phosphide tablets are used to control borers, soil should be used to seal wormholes.
Specific insect growth regulators can be divided into the following categories according to their different roles:
1) Insect growth regulator, a kind of insecticide, enters the insect body through stomach poisoning or contact killing, hinders the formation of chitin, affects the formation of inner epidermis, prevents the smooth progress of molting and metamorphosis of insects, hinders the hatching of eggs and the emergence of adults or malformations of insects, thus exerting insecticidal effects. This kind of medicine has high activity, low toxicity, less residue, obvious selectivity, and is beneficial to human, livestock and other biological safety. But the insecticidal effect is slow and the residual period is short. Such as Metroxazole No. 3, Youlede, Yitaibao, Deworming Urea and so on.
2) Attractants lure pests together to annihilate with trace gaseous molecules. This kind of medicine can be divided into three kinds: food attractant, sex attractant and oviposition attractant. Among them, sex attractants are widely used. Such as sex attractants of peach carnivorous insects and grape winged moth.
3) The repellent acts on the protected objects, making the pests unwilling to approach or transfer or escape to imagine, so as to achieve the purpose of protecting the pests. Such as mosquito repellent oil, camphor, etc.
4) After the insecticide is eaten by the pest, the normal physiological function of the ring-breaking pest reduces or stops feeding quickly, and finally causes the pest to starve and die. Such as azadirachtin, antifeedant amines, etc.
These insecticides are not very toxic in themselves, but act on insects with special properties. These pesticides are generally referred to as specific pesticides.
(1) Protective fungicides sprayed on the surface of plants before pathogenic microorganisms invaded the host plants, forming a protective film, which hindered the infection of pathogenic microorganisms and thus protected the plants from their harm. Such as Bordeaux liquid, Dayson zinc, Dasheng, etc.
(2) Therapeutic fungicides pathogenic microorganisms have invaded plants and sprayed medicines during their incubation period in order to inhibit their continued expansion or eliminate their harmful effects in plants. Such as triazolone, thiophanate methyl, ethyl phosphorus and aluminium, etc.
(3) Eradicative fungicides have direct and strong killing effect on pathogenic microorganisms. This kind of medicament is often intolerable for plant growth, so it is generally only used for soil treatment before sowing, plant dormancy or seedling treatment. Such as Shi Sulfur Mixture, Fumei arsenic and so on.
Selective herbicides are selective among different plants, that is, they can poison or kill some plants, but are safer to others. Most herbicides are selective herbicides. Such herbicides as herbicide herbicide, dichlorfon and so on belong to this kind of herbicide.
(2) Intoxicant herbicides such as herbicides lack selectivity to plants, or have little selectivity, which can kill most of the green plants. It can kill both weeds and crops, so it should be used with great caution. Paraquat and glyphosate belong to this kind of herbicide. Generally, it can be used for weeding in recreational areas, fields and embankments. Generally, directional spraying is used for weeding in fields.
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