Which statement best describes the purpose of rotating pesticide modes of action in turf IPM and a basic guideline?

• A. To maximize speed of kill
• B. To prevent resistance development; rotate modes of action and avoid repeating the same chemical class too frequently.
• C. To minimize environmental contamination; rotate by application method
• D. To reduce cost; rotate by brand name

Answer: (B)

Rotating modes of action is a resistance-management strategy in turf IPM. When the same chemical class is used repeatedly, pests that have or acquire even low levels of resistance survive and multiply, making the product less effective over time. Switching to pesticides with different modes of action in successive applications changes the selective pressure on the pest population, slowing the evolution of resistance and helping maintain control in the long term. The basic guideline to avoid repeating the same chemical class too frequently reinforces this approach because it keeps the pest population from quickly becoming resistant to a single MOA. In turf systems, this concept is part of a broader practice of integrating chemical choices with monitoring and nonchemical methods to sustain efficacy while reducing environmental impact. The other ideas miss the point: maximizing speed of kill focuses on immediate action and can drive rapid resistance if the same MOA is used again; rotating by application method or by brand name does not ensure switching MOAs and can give a false sense of protection against resistance.