Why the more pesticides are used, the more ineffective they become.

A kind of medicine, at the beginning of use, the insecticidal effect is often very good, but with the increasing dosage and the continuous expansion of the scope of use, cases of drug resistance continue to appear. The most prominent is cis-fenvalerate, which is often called "righteous Laifuling" in advertisements in the 1980s, but justice can no longer be done, because even if the dosage or concentration of medicine is increased by dozens or even hundreds of times, the pests cannot be killed. This is actually because pests develop drug resistance, which is the ability to endure the dose of drugs that kill most individuals in a normal population and develop in their populations. In fact, there are already individuals with different degrees of sensitivity to pesticides in the population of natural pests. The process of using insecticides is actually a process in which insecticides play a selective role in insect populations. Each use of pesticides will leave relatively drug-resistant individuals, kill relatively sensitive individuals, after the survival of the fittest, but also improve the level of drug resistance of insect pests. It has been found that: (1) the emergence of drug resistance is related to pests and their living habits. Pests with short life history, more reproductive generations each year and more exposure to pesticides, such as mites, shellfish, aphids, mosquitoes and so on, are most likely to produce resistant populations. (2) A pest is resistant to a pesticide and is often resistant to other pesticides of the same type, and this interaction is not easy to occur among drugs with different insecticidal mechanisms. (3) if the same pesticide is used continuously for many times or the treatment concentration is high, the resistance is formed quickly, and vice versa. Generally speaking, first of all, the rise of drug resistance of insect pests can be prevented or delayed through rational use of drugs. For this reason, it is advocated to adopt a variety of comprehensive control techniques, including breeding, popularizing resistant varieties, improving cultivation techniques, carrying out biological and physical control, so as to reduce the times and dosage of chemical control as much as possible. Secondly, the mixed use, rotation and mosaic application of pesticides with different action mechanisms are selected. Thirdly, it is to improve the pesticide application technology, such as symptomatic medication, timely spraying, selection of efficient machines and tools, spraying in place and so on, so as to improve the killing effect as much as possible.