How can pesticide resistance develop in pests?

Pesticide resistance develops primarily due to the overuse or misuse of pesticides, which apply selective pressure on pest populations. When pesticides are used extensively or incorrectly, a situation arises where pests that have a natural mutation or genetic trait that provides resistance to the chemical survive and reproduce. This selective survival leads to an increase in the proportion of resistant individuals in the pest population. Over time, repeated exposure to the same pesticide can thus result in a population consisting predominantly of resistant pests, rendering the pesticide less effective or completely ineffective against that specific pest.

In contrast, while increased pest populations or survival rates can contribute to resistance, it's the selective pressure from pesticide use that primarily drives the resistance phenomenon. The introduction of biological control methods generally promotes a broader ecological balance and does not usually lead to pesticide resistance. Changes in environmental conditions may impact pest populations in various ways, but they do not directly cause the genetic resistance seen with pesticide exposure.