Insects, like other living organisms, can develop resistance to the action of certain preparations. Cross-resistance or cross-resistance is the ability of pests to adapt to the effects of chemical insecticides that have a common mechanism of action.
A population of insects in terms of resistance to a particular preparation can be displayed in the form of a "Gaussian bell": 1) a small number of individuals in the population of the pest will die under the influence of any amount of the preparation; 2) on the other hand, there will be a small number of individuals that will not die at the action of any amount of the preparation; 3) the bulk of the population consists of persons who will die more in the event of an increase in the concentration of the active substance. When treated with this insecticide, less stable individuals will die first. Subsequent treatment will ruin a few more individuals that are already less sensitive. If you continue to use only one preparation, then only those who are completely not sensitive to it will remain. For example, Coragens and Fame cause cross-resistance in Tuta Absoluta, that is, the treatment as one and the other preparation has a similar effect on the pest.
The pest does not feel the difference between treatments with these two different preparations. If we continue to use only these two preparations, only stable individuals will remain in the phytophage population, which will not be affected by these insecticides. Usually, those who are more sensitive to the preparation have other advantages, for example, they have a higher reproductive rate, compared with those resistant to this active substance, population representatives. That is, after several treatments with one drug for some time, the rate of population growth will be low. However, on the other hand, the population will still increase, and the sensitivity to this active substance will not recover. Therefore, it is necessary to use preparations that have different mechanism of action on the pest. Thus, the pest's sensitivity to each individual preparation remains at the same level, but it is possible to control the population of its population. After a sufficient period of time, it will be possible to apply the same preparation and to receive high efficiency from treatment.
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