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Management Updates: August 28, 2023

Dollar Spot Resistance Assays
August 28, 2023

If you’re managing golf course turf, it’s likely that summer fatigue from battling dollar spot is bringing you down. Unfortunately, we're not out of the woods yet, with a few more months of wrestling ahead, as well as the potential for a dreaded “fall resurgence”. Dollar spot reigns as a top economic burden and wreaker of havoc for golf courses throughout the New England region. To control this pesky problem, repeated application of fungicides is the most effective and reliable method. However, the major drawback of relying on chemicals is the development of resistance, which can render fungicides partially or completely ineffective in the field. The occurrence of resistance limits the management options available to superintendents. With limited choices, superintendents are forced to repeatedly apply the same type of fungicide, further diminishing available resources. It's a frustrating situation, as this summer's muggy weather and frequent rain only exacerbate the dollar spot issue. Such conditions heighten pathogen populations and increase the likelihood of encountering a resistant population. In-vitro sensitivity assays from regional golf courses this year have revealed populations with resistance to four major fungicide classes (DMI, SDHI, dicarboximide, benzimidazole) and insensitivity to fluazinam.

Dollar spot resistance assays are available to determine the effectiveness of various fungicides. The UMass Turf Pathology Lab provides fee-based in-vitro sensitivity assays to golf course superintendents and the turf industry for the five fungicide classes mentioned above. Based on the sensitivity profile, intrinsic efficacy, and resistance pattern, the lab offers fungicide recommendations tailored to your golf course.

Effective management of the late summer wave (“fall resurgence”) of dollar spot can reduce the primary source of infection for the following year and alleviate disease pressure. This leftover wave, characterized by increasing incidence of dollar spot, normally occurs from late summer to early fall, in August or September. It is important to note that high disease pressure can impact the efficacy of fungicides in the field, potentially leading to ineffective control. Therefore, in-vitro sensitivity assays remain necessary. Knowing the sensitivity profile of fungicides on fairways can save hundreds of dollars. Remember, prevention is the most effective form of treatment.

Should you encounter decrease in control effectiveness (such as a decrease in application interval) while using the fungicides mentioned earlier, consider providing samples to the UMass Turf Pathology Lab. In addition to informing your management program, submitting samples will also aid us in ongoing research and monitoring of resistant populations. If you have interest in this service or have questions regarding dollar spot resistance assays, we urge you to get in touch with Mr. Soonhong Min at or Dr. Geunhwa Jung at


Submitted by: Dr. Geunhwa Jung and Soonhong Min, Graduate Student, Jung Lab