What is the purpose of rotating pesticides with different modes of action (MOA)?

• A. To reduce cost
• B. To delay resistance development in pests by reducing selection pressure on a single MOA
• C. To simplify labeling
• D. To shorten the post-application interval

Answer: (B)

Rotating pesticides with different modes of action is used to slow resistance development in pests by avoiding giving the same target the same selective pressure over time. When a pest population is repeatedly exposed to products that all act the same way, individuals with natural tolerance or mutations for that MOA survive and reproduce, and the resistance trait spreads. By switching to products that affect pests in a different way, those already resistant to one MOA don’t have an advantage against the next product, so resistance frequency rises more slowly. This approach helps keep multiple control options effective longer and is a core part of resistance management within integrated pest management.

The other options aren’t about resistance dynamics: rotating MOAs isn’t primarily about reducing cost, simplifying labeling, or shortening the post-application interval.