Resistance develops faster when?

• A. Rotating modes of action
• B. Pests are never exposed
• C. Using lower doses
• D. Same pesticide is used repeatedly

Answer: (D)

Resistance only appears when pests are exposed to a pesticide and the exposure creates selection pressure. Using the same pesticide repeatedly gives a constant, uniform challenge, so individuals that happen to have resistance survive each application and reproduce. Over generations, the resistance traits become common, making the pesticide ineffective faster than with other strategies. Rotating modes of action changes the target mechanism and reduces the consistent pressure on any single resistance gene, slowing the spread. Sublethal dosing can also encourage resistance by allowing partially resistant individuals to survive, but repeated, identical exposure is the most direct way to drive rapid resistance. If pests were never exposed, there would be no selection for resistance at all.