In this episode of Turfgrass Epistemology, I discuss the peer-reviewed article “Dollar Spot and Gray Leaf Spot Severity as Influenced by Irrigation, Chlorothalonil, Paclobutrazol, and a Wetting Agent” by McDonald, Dernoeden, and Bigelow (2006), published in Crop Science.

This landmark study examines how irrigation regime, soil moisture, and common management inputs influence dollar spot and gray leaf spot development on creeping bentgrass and perennial ryegrass fairways. I explain why dollar spot was consistently more severe under dry, infrequently irrigated conditions, how soil moisture strongly influenced disease severity late in the season, and what this means for cultural disease management strategies on golf courses.

The discussion also covers how chlorothalonil performance varied with irrigation regime, why paclobutrazol provided partial dollar spot suppression, and why wetting agents alone were unreliable for disease control. Most importantly, I explain how this paper reshapes the way we should think about water management as a disease driver, rather than viewing irrigation only through the lens of turf stress or playability.

If you manage creeping bentgrass fairways, battle chronic dollar spot, or want an evidence-based explanation of how irrigation practices interact with fungicides and plant growth regulators, this video walks through what the data actually show—and how to apply it responsibly in modern turfgrass management.

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