What is the rationale behind rotating insecticide modes of action?

• A. To maximize immediate kill
• B. To reduce residues quickly
• C. To delay or prevent resistance development
• D. To minimize costs

Answer: (C)

Rotating insecticide modes of action slows or prevents resistance by reducing selection pressure on pest populations. When the same mode of action is used repeatedly, individuals with resistance traits survive and reproduce, leading to a population that’s harder to control. Switching to different modes means the pest must develop multiple resistance traits to stay alive, which is much less likely and slows the spread of resistance. This approach also helps avoid cross-resistance where resistance to one mode reduces effectiveness of similar ones. In practice, resistance management is most effective when rotation is combined with monitoring, proper timing, accurate labeling, and other integrated pest management strategies, rather than aiming for immediate, maximum kill or lower costs.