What is fungicide resistance and how can it be delayed in turf management?

• A. Increased potency of a fungicide over time
• B. Fungicides becoming cheaper
• C. Reduced sensitivity of pathogens to a fungicide due to excessive or repeated use; delay by rotating modes of action, using integrated cultural controls, and avoiding overuse of a single product
• D. Fungicide resistance cannot be delayed

Answer: (C)

Fungicide resistance happens when a pathogen population gradually becomes less affected by a chemical because repeated exposure selects for individuals with reduced sensitivity. Over time these tolerant individuals dominate, making the fungicide seem less effective. In turf management, this resistance can be delayed by rotating modes of action—using fungicides from different chemical families so the pathogen isn’t constantly exposed to one target. Pair this with integrated cultural controls that reduce disease pressure, such as proper irrigation and drainage to minimize leaf wetness, appropriate mowing height and turf vigor, improved sanitation, and aeration or thatch management. Also avoid overusing a single product or applying sublethal doses, and follow label guidelines for timing and rates to keep selection pressure low. The other ideas—fungicides becoming cheaper, or potency increasing over time, or the claim that resistance cannot be delayed—don’t describe how resistance develops or how it can be managed in the real world.