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Insecticides and Metabolite Standards

November 23, 2022


Introduction to Insecticides


Insecticides are a class of chemicals mainly used to control agricultural pests and urban sanitation pests. The use of insecticides has a long history, a large amount and a variety of varieties, which have played an extremely important role in increasing agricultural production.


1. Classification of Insecticides

1.1 Source

 According to the source classification, insecticides can be divided into two categories: biologically derived insecticides and chemically synthesized insecticides.

 Biological insecticides include preparations of insecticidal active ingredients extracted from higher plants (such as natural pyrethrins, rotenone, etc.), insecticides made from living microorganisms (fungi, bacteria, and viruses), insect physiologically active substances (such as pheromones, etc.).

 Chemically synthesized insecticides include inorganic insecticides (such as inorganic arsenic, inorganic fluorine, inorganic sulfur preparations, etc.), organic insecticides (organochlorine, organophosphate, carbamates, and pyrethroidsetc.).


1.2 Toxicological Effects

 According to their toxicological effects, insecticides can be divided into four categories: neurotoxic insecticides, respiratory toxicity insecticides, physical insecticides, and specific insecticides.

 Neurotoxic insecticides (such as pyrethrins, etc.) mainly act on the nervous system of pests, interfere with and destroy the neurophysiological and biochemical processes of pests and cause insect poisoning and death. organophosphate, carbamate, and pyrethroid insecticides are all nerve agents.

 Respiratory toxic insecticides, after contacting with pests, have an inhibitory effect on a certain part of the respiratory chain due to physical or chemical effects, causing the pests to suffocate and die due to obstacles to their respiration.

 Physical insecticides destroy pests through physical action. Mineral oils, for example, can clog pest valves. The inert powder can grind the skin of the pests and cause the pests to die.

 Specific insecticides have long-term effects on the physiological behavior of pests, making them unable to continue to reproduce. Specific insecticides include the following five categories: attractants, repellants, antifeedants, sterile agents, and insect growth regulators. Attractants attract pests by sex or bait. Repellents keep pests away from where the drug is. Antifeedants inhibit the taste of pests, resulting in antifeeding reactions that lead to starvation and death. Sterile agents destroy the reproductive function of pests. Insect growth regulators eventually lead to the death of pests by inhibiting the physiological development of pests, such as inhibiting molting and new epidermis formation, feeding, etc.


1.3 Mode of Action

 The main ways that insecticides can kill pests are:

 Contact Poisons: After the insecticide comes into contact with the pest, it enters the body through the epidermis of the pest to play a role, causing the pest to be poisoned or suffocated to death.

 Stomach Poisons: Insecticides are directly absorbed by the insects after being eaten by the gastrointestinal tract, causing them to be poisoned and die.

 Fumigants: Insecticides are vaporized from solid or liquid into gas, and enter the body through the respiratory system of the pest in a gaseous state, causing it to be poisoned and die.

 Inhalation: Insecticides are absorbed by leaves or roots of plants and transmitted to the whole plant. Poisoning and death when pests eat.

 Antifeeding: After the insecticide is eaten by the pest, it will cause the destruction of the normal physiological function of the pest, and eventually lead to the starvation and death of the pest.

 Avoidance: The gas molecules volatilized by the insecticides stimulate the olfactory organs of the pests within a certain range and make them escape from the scene.

 Attraction: The opposite of avoidance. Insecticides attract pests to the location of the drug through feeding lures, egg-laying lures, and sexual lures.

 Sterility: Insecticides cause pests to lose their normal reproductive function by destroying their reproductive systems.

 Growth regulation: Insecticides prevent or inhibit the normal growth and development of pests, making them lose their ability to harm or even die.


2. Common Insecticides

2.1 Organochlorine Insecticides

 Organochlorine insecticides are a class of chlorine-containing organic synthetic insecticides with excellent insecticidal effects. Most organochlorine insecticides have the characteristics of low production cost and long-term residual in animals and plants and in the environment.


2.2 Organophosphate Insecticides

 Organophosphate insecticides have the advantages of easy degradation and little pollution, and the insecticidal effect increases with the increase of temperature. Most organophosphate insecticides are broad-spectrum insecticides. The insecticidal ability of organophosphate insecticides is very strong, its ability is stronger than that of organochlorine insecticides, stronger than or equivalent to carbamates, but weaker than pyrethroid insecticides. The mechanism of action is to inhibit the activity of cholinesterase in the pests so that the acetylcholine that transmits the nerve impulses of the pests cannot be hydrolyzed and accumulated in time, thereby destroying the normal conduction of the nervous system, causing a series of nervous system poisoning symptoms, and finally leading to the death of the insects. Its insecticidal modes of action are diverse, including fumigation, contact, stomach poisoning, and inhalation.


2.3 Carbamate Insecticides

 Carbamate insecticides are highly efficient and broad-spectrum, non-irritating to humans and have no impact on the environment, and are widely used in daily life and agricultural production. Its mechanism is similar to that of organophosphate insecticides. Insecticide compound molecules combine with cholinesterase, inhibit the activity of cholinesterase, block normal nerve conduction, and then cause pest poisoning.


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