What causes resistance?

• A. Genetic mutation spontaneously
• B. Repeated use of same pesticide
• C. Pests migrate to new areas
• D. Pesticide breaks down quickly

Answer: (B)

Repeated exposure to the same pesticide creates selection pressure. Within a pest population, there’s natural genetic variation, so a few individuals may naturally tolerate the chemical. When you continuously apply the same pesticide, those tolerant pests survive and reproduce, passing on their resistance traits. Over time, the resistant traits become common, making the pesticide less effective. This is why repeated use drives resistance.

Genetic mutations can provide resistance, but the repeated-use pattern is what amplifies those variants. Pests migrating to new areas doesn’t by itself create resistance, and a pesticide that breaks down quickly reduces, rather than promotes, the selection for resistant individuals.