Why do insecticides become less and less effective the more you use them?
Chlorpyrifos is a highly effective, broad-spectrum organophosphorus insecticide that acts on pests through contact toxicity, stomach toxicity and fumigation, and is especially effective against the brown planthopper. The relevant application techniques are described below: 1. Product characteristics: 1. Chlorpyrifos is currently available in China in formulations such as emulsifiable concentrate, granules and microemulsion. Among them...
A pesticide often works very well when first used, but as the dosage keeps increasing and the scope of use keeps expanding, cases of rising resistance keep appearing. The most striking example is cis-fenvalerate, the "righteous Fenvalerate" often mentioned in 1980s advertisements, which can no longer uphold justice, because even raising the dose or spray concentration by dozens of times or even hundreds or thousands of times cannot kill the pests. This is actually because the pests have developed resistance, that is, the ability to tolerate a dose that kills most individuals in a normal population and to develop within that population. In fact, pest populations in nature already contain individuals with different levels of sensitivity to pesticides. The process of using insecticides is in effect a process in which the insecticide exerts selective pressure on the insect population. Each application of an insecticide leaves behind the relatively resistant individuals and kills the relatively sensitive ones, and after this survival of the fittest, the resistance level of the pest population also rises.
It has now been established that: (1) The development of resistance is related to the pest and its living habits. Pests with short life cycles, many generations per year and frequent exposure to pesticides, such as mites, scale insects, aphids and mosquitoes, are the most prone to developing resistant populations. (2) When a pest develops resistance to one pesticide, it is often also resistant to other pesticides of the same type, while this cross-interaction is unlikely to occur between drugs with different insecticidal mechanisms. (3) The more times the same pesticide is used continuously or the higher the treatment concentration, the faster resistance forms, and vice versa.
Generally speaking, resistance in pests can first be prevented or slowed through rational pesticide use. For this reason, it is advocated to adopt comprehensive control using multiple techniques, including breeding and promotion of resistant varieties, improved cultivation techniques, and biological and physical methods, so as to minimize the number of chemical control applications and the dosage. Second, choose insecticides with different mechanisms of action for mixing, rotation and mosaic application. Third, improve application techniques, such as using the right pesticide for the right target, spraying at the right time, choosing efficient equipment, and applying the spray thoroughly, so as to maximize the killing effect.