Do pesticides cause resistance

The resistant individuals are present in the population before the pesticide is introduced. By careful testing for resistance in wild populations that have never been exposed to insecticides, it has been possible to detect some resistant individuals. 

An indirect proof that insecticides do not cause resistance is shown with sister selections. It was demonstrated that it is possible to make resistant strains by breeding pairs of insects separately. Some of the offspring were used for resistance testing, and the brothers and sisters of insects with low susceptibility were taken for breeding. By this method it was possible to produce resistant strains from insects that had never themselves, nor their ancestors, been exposed to insecticides. 

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