What can lead to resistance when using insecticides?

Excessive application and lack of variety in pesticides can significantly contribute to the development of resistance among pest populations. When the same insecticide is used repeatedly and excessively, insects that are susceptible to the chemical are killed off, while only the individuals that possess resistance mechanisms survive. This selective pressure leads to a situation where the resistant individuals are able to reproduce, resulting in a population that is increasingly composed of resistant pests.

Additionally, relying on a limited number of pesticide modes of action reduces the chances of effectively managing pest populations over time. In contrast, employing a rotation of different insecticides with varying mechanisms can mitigate the likelihood of resistance, as it disrupts the selection process favoring resistant pests. This strategy ensures that any remaining susceptible individuals are targeted with different modes of action, reducing the chances for resistance to develop.

The other options, such as infrequent use and minimal exposure, would generally lead to less selection pressure and could actually slow down the resistance development. Natural pest population growth does not inherently cause resistance unless coupled with excessive use of specific pesticides. Improper storage might affect the effectiveness of pesticides but is not a direct contributor to the resistance development seen with frequent and uniform pesticide application.