Synthetic chemical pesticides can be divided into organic chlorine, organic phosphorus, organic mercury, organic arsenic, carbamate and other preparations according to their chemical composition. According to the physical state of pesticides in the environment, they can be divided into powder, soluble liquid and volatile. Liquid, etc.; according to its mode of action, there may be stomach poisoning, contact killing, fumigation, and the like.
Diseases, insects, weeds and other pests vary greatly in terms of morphology, behavior, and physiological metabolism. Therefore, a pesticide can only control a certain kind of pests and diseases, and the specificity is very strong.
1. Organochlorine pesticides
Most of these pesticides are chlorinated derivatives containing one or several benzene rings. The most important varieties are DDT and 666, followed by aldrin, dieldrin and endrin. The characteristics of organochlorine pesticides are: stable chemical properties, long residual time in the environment, not easy to decompose in a short period of time, soluble in fat, and accumulated in fat. Long-term use is the most important type of pesticide causing environmental pollution. At present, many countries have banned use. China has banned production and use in 1985.
2. Organophosphorus pesticides
Organophosphorus pesticides are organic compounds containing phosphorus, and some also contain sulfur and nitrogen, most of which are phosphates or amides. Generally, it is highly toxic, but it is easy to decompose. It has a short residual time in the environment. In the animal and plant, the phosphate ester is not easily accumulated due to the action of the enzyme, so it is often considered to be a safer pesticide. Organophosphorus pesticides can be toxic to insect mammals, destroying the secretion of acetylcholine by nerve cells, hindering the physiological functions of the stimulating transport function, and causing death. Therefore, the environmental pollution toxicity of organophosphorus pesticides in the short term is still not negligible. Many research reports this year have pointed out that organophosphorus pesticides have alkylation effects, which may cause carcinogenic and mutagenic effects in animals.
3. Carbamate pesticides
These pesticides all have the structure of phenyl-N-alkyl formate. Like organophosphorus pesticides, they have anti-cholinesterase activity and the same symptoms of poisoning, but the mechanism of poisoning is different. It is easily decomposed in the environment and can be rapidly metabolized in animals. The toxicity of metabolites is mostly lower than its own toxicity, so it is a low-residue pesticide.
4. Herbicides (except herbicides)
Herbicides are selective and can only kill weeds without harming the crop. The most commonly used herbicides are 24-D (24-dichlorophenylacetic acid) and 245-T (245-trichlorophenoxyacetic acid) and their lipids, which can eliminate many broadleaf grasses, but many Leaf grass is harmless and is a mediating substance. Some are non-selective to kill plants that come into contact with the agent, such as sodium hypochlorite. Some varieties only work on the parts that the agent touches, and the agent does not transfer in the plant body and does not conduct. Most herbicides are gradually decomposed in the environment, have no interference with the biochemical processes of mammals, are not very toxic to humans and animals, and have not been found to accumulate in humans and animals.
Diseases, insects, weeds and other pests vary greatly in terms of morphology, behavior, and physiological metabolism. Therefore, a pesticide can only control a certain kind of pests and diseases, and the specificity is very strong.
1. Organochlorine pesticides
Most of these pesticides are chlorinated derivatives containing one or several benzene rings. The most important varieties are DDT and 666, followed by aldrin, dieldrin and endrin. The characteristics of organochlorine pesticides are: stable chemical properties, long residual time in the environment, not easy to decompose in a short period of time, soluble in fat, and accumulated in fat. Long-term use is the most important type of pesticide causing environmental pollution. At present, many countries have banned use. China has banned production and use in 1985.
2. Organophosphorus pesticides
Organophosphorus pesticides are organic compounds containing phosphorus, and some also contain sulfur and nitrogen, most of which are phosphates or amides. Generally, it is highly toxic, but it is easy to decompose. It has a short residual time in the environment. In the animal and plant, the phosphate ester is not easily accumulated due to the action of the enzyme, so it is often considered to be a safer pesticide. Organophosphorus pesticides can be toxic to insect mammals, destroying the secretion of acetylcholine by nerve cells, hindering the physiological functions of the stimulating transport function, and causing death. Therefore, the environmental pollution toxicity of organophosphorus pesticides in the short term is still not negligible. Many research reports this year have pointed out that organophosphorus pesticides have alkylation effects, which may cause carcinogenic and mutagenic effects in animals.
3. Carbamate pesticides
These pesticides all have the structure of phenyl-N-alkyl formate. Like organophosphorus pesticides, they have anti-cholinesterase activity and the same symptoms of poisoning, but the mechanism of poisoning is different. It is easily decomposed in the environment and can be rapidly metabolized in animals. The toxicity of metabolites is mostly lower than its own toxicity, so it is a low-residue pesticide.
4. Herbicides (except herbicides)
Herbicides are selective and can only kill weeds without harming the crop. The most commonly used herbicides are 24-D (24-dichlorophenylacetic acid) and 245-T (245-trichlorophenoxyacetic acid) and their lipids, which can eliminate many broadleaf grasses, but many Leaf grass is harmless and is a mediating substance. Some are non-selective to kill plants that come into contact with the agent, such as sodium hypochlorite. Some varieties only work on the parts that the agent touches, and the agent does not transfer in the plant body and does not conduct. Most herbicides are gradually decomposed in the environment, have no interference with the biochemical processes of mammals, are not very toxic to humans and animals, and have not been found to accumulate in humans and animals.
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