What primarily causes the development of resistance in pests?

The primary cause of resistance development in pests is the continued use of the same pesticide or similar classes of pesticides over time. When a specific pesticide is repeatedly applied, it selectively kills the susceptible individuals in a pest population while allowing those with genetic mutations that confer resistance to survive and reproduce. Over multiple generations, this can lead to a higher proportion of resistant individuals within the population, effectively rendering the pesticide less effective.

In contrast, using diverse pesticides can help mitigate resistance development because it reduces the likelihood that pests will be exposed consistently to the same mode of action, thereby preventing the selection pressure that leads to resistance. Random genetic mutations do contribute to the overall genetic variability in pest populations but do not in themselves cause resistance; rather, it is the selective pressure exerted by pesticide use that favors the survival of resistant individuals. Environmental changes can affect pest populations and their dynamics but are not the primary driver of resistance development linked to pesticide usage.