What is a general reason to rotate fungicides with different modes of action on turf?

• A. To speed up growth of fungi
• B. To reduce application rate
• C. To help prevent the development of resistant pathogens and maintain efficacy
• D. To make record-keeping easier

Answer: (C)

Rotating fungicides with different modes of action helps keep turf diseases under control over the long term by preventing the pathogens from becoming resistant. When the same mode of action is used repeatedly, fungi that have or develop tolerance to that mode survive and reproduce, leading to a resistant population and reduced effectiveness. Switching to products that attack the pathogen in a different way means those resistant individuals are less likely to survive the next treatment, slowing or stopping resistance from spreading. Rotating across different modes also lowers the chance of cross‑resistance, where resistance to one product confers resistance to others in the same class. This approach preserves the efficacy of fungicides and helps maintain disease control throughout the season. It’s not about speeding growth, reducing the amount of product needed per application, or making record-keeping easier.