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.
Classification of Insecticides
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 pyrethroids, etc.).
- 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. 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.
- 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.
- 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.
Organochlorine Insecticides and Metabolite Standards
- 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.
Organophosphate Insecticides and Metabolite Standards
- 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.
Carbamate Insecticides and Metabolite Standards
Nereistoxin insecticides have the characteristics of broad spectrum, high efficiency, low toxicity, and various modes of action. Nereistoxin insecticides have strong contact and stomach poisoning effects on pests, and also have antifeedant, inhalation and fumigation effects.
Pyrethroids are a class of organic synthetic insecticides with important properties such as high efficiency, broad spectrum, low toxicity and biodegradability. Its insecticidal ability is 10-100 times higher than that of organochlorine, organophosphate and carbamate insecticides. The mechanism of action is to interfere with the sodium ion channel between the sensory nerve and the connecting nerve, hinder the transmission of nerve signals, and eventually lead to the poisoning and death of pests.
Pyrethroid Insecticides and Metabolite Standards
Neonicotinoids are highly potent and broad-spectrum insecticides with low toxicity to mammals. Neonicotinoids have little or no cross-resistance to traditional insecticides (such as pyrethroids, organophosphate and carbamates, etc.) pests with long-term resistance to insecticides). The mechanism of action is mainly to act on the central nervous system of insects as an agonist of nicotinic acetylcholine receptors (nAChRs), blocking the normal conduction of the central nervous system, resulting in paralysis and death of pests.
Neonicotinoid Insecticides and Metabolite Standards