How can pests become resistant to pesticides?

Pests can become resistant to pesticides primarily through the process of natural selection. When a pesticide is applied, it may kill a large portion of a pest population, but some individuals may possess genetic traits that provide resistance to that specific pesticide. These resistant individuals are more likely to survive and reproduce, passing on their resistance traits to the next generation. Over time, this can lead to a population that is predominantly resistant to the pesticide, making the chemical much less effective.

In contrast, genetic modification in a laboratory is not a natural process that occurs in the environment, and it does not explain resistance development in wild populations. Exposure to multiple pesticides concurrently might actually reduce the chances of developing resistance, as it applies selection pressure from different angles. Isolation from pesticides could delay the development of resistance but would not cause it; rather, it may allow for the recovery of susceptibility if the resistance traits are not expressed without selection pressure. Thus, the mechanism of natural selection is the key driver in the evolution of pesticide resistance in pest populations.