What causes resistance to pesticides?

• A. Using the same pesticides over and over.
• B. Applying pesticides only when pests are present.
• C. Rotating pesticides after every application.
• D. Using biological controls exclusively.

Answer: (A)

Pesticide resistance happens when pests are exposed repeatedly to the same chemical, creating strong selection pressure. Susceptible individuals are killed, while those with resistant traits survive and reproduce. Over many generations, the resistant traits become common, making the pesticide less effective. Rotating pesticides with different modes of action helps prevent this by changing the selection pressure, and using pests controls alongside chemicals or applying pesticides only when pests are present can reduce overall exposure. But the direct cause of resistance is the repeated, constant use of the same pesticide, which allows resistant individuals to dominate the population.