Dollar Spot Disease Forecasting Study at Rocky Ford Turfgrass Research Center

By Teresa Roberts

Wednesday, July 8, 2026

By Megan Kennelly, KSU Plant Pathology

Dollar spot is a common fungal disease in golf course creeping bentgrass putting greens and fairways. In low-cut turf, the disease appears as sunken patches of tan to brown turf 1-2 inches in diameter (about the size of a silver dollar, which gave the disease its name).

Dollar spot causes tan patches 1-2 inches across

In taller turf the blighted spots are somewhat larger. On dewy mornings, white, cobwebby fungal growth is sometimes visible in the turf.

On dewy mornings, white fungal growth may be present

Fungicides are commonly used to control dollar spot, and it is a research goal to reduce these inputs. There has been research to understand how to use weather-based information to optimize the timing of fungicide applications. In addition, turfgrass breeders have developed turf varieties with reduced susceptibility. How can we combine knowledge of dollar spot biology and host resistance to reduce fungicide applications while maintaining strong disease control?

Here at KSU we are collaborating with researchers in several other states to investigate this question. At Rocky Ford, we have an experiment with three varieties of creeping bentgrass (Coho, Shark, and Penncross) with different levels of susceptibility to dollar spot. We are using the weather-based forecasting model (the Smith-Kerns model – click here for all the details) which determines different thresholds of disease risk. We apply fungicides to the different varieties based on various thresholds, assessing disease every 1-2 weeks. To monitor the risk thresholds we use the online Greencast tool here, typing in our zip code. This is our second year studying the exact current treatments. At the end of the season, we will send our data to the project coordinator (Dr. Paul Koch at UW-Madison) for statistical analysis with all our partner states. In both 2025 and again so far in 2026 we are seeing that the more resistant variety (Coho) can withstand a lot higher disease pressure than the others, with clear differences between threshold treatments.

Variation in dollar spot severity is visible in different fungicide regimes

Stay tuned for more information! The goal is to develop ways to manage disease with fewer chemical inputs. In the meantime, if you want to monitor dollar spot disease risk in your area you can use the tool online yourself. Finally, for an excellent source of information about fungicides for dollar spot (and other turf diseases) you can check out this online reference which is based on studies done all across the country.