Fungicides intended to suppress turfgrass diseases may damage fairways

(Press-News.org) UNIVERSITY PARK, Pa. — Golf course managers have much more insight into which fungicides to use to suppress turfgrass diseases, such as the common and costly dollar spot disease, without damaging the grass on their fairways, thanks to a new study by researchers at Penn State.

The team evaluated variation in turfgrass injury caused by nine commercially available demethylation inhibitor (DMI) fungicides — a class of fungicide widely used in turfgrass management — commonly used to suppress dollar spot and other major turfgrass diseases when applied to annual bluegrass and creeping bentgrass fairways. In Pennsylvania and much of the Northeast, golf course fairways often are a mix of creeping bentgrass and annual bluegrass.

In findings  published online ahead of inclusion in a printed edition of International Turfgrass Society Research Journal, the researchers reported that two of the fungicides, metconazole and triticonazole, result in injury to annual bluegrass but not creeping bentgrass. And another fungicide, mefentrifluconazole, resulted in the lowest injury on both annual bluegrass and creeping bentgrass.

This research was driven by the need to better understand the turf safety of both older and newer DMI fungicides that are commonly used on golf courses, according to John Kaminski, professor of turfgrass science in the College of Agricultural Sciences and senior author on the study.

“While these products are highly effective for disease control, their potential to cause injury to different turfgrass species — especially under varying environmental and management conditions — hasn’t been systematically studied,” he said. “Golf course superintendents have long relied on anecdotal experience or manufacturer guidance, but there’s been no side-by-side comparison that puts all of these fungicides through the same testing protocols.”

In 2020, two field trials were conducted on research fairways at Penn State’s Valentine Turfgrass Research Centre, located at University Park. Nine fungicides were applied in 14-day intervals over three summer months. The trials were repeated in 2021. The researchers applied nine fungicides to the research fairways and monitored the turfgrass for ill effects: propiconazole, triadimefon, myclobutanil, mefentrifluconazole, pydiflumetofen, flutriafol, tebuconazole, metconazole and triticonazole.

Study first author Maureen Kahiu, who earned her master’s degree from Penn State with this research project, applied all the fungicides to the research fairways with a backpack hand sprayer. To determine any phytotoxicity, or evidence of toxic effects, caused by the fungicide treatments, Kahiu examined the plots on a daily basis, looking for turfgrass injury, based on deviations in color, texture, density and growth.

A former golf course superintendent for three years in her native Kenya, Kahiu came to Penn State to study in the turfgrass science program with Kaminski as her adviser, after meeting him at an international golf industry show. She said the vaunted reputation of Penn State’s turfgrass science program attracted her.

“Anywhere you go in the world, when it comes to turfgrass management, Penn State is where you want to be. It's known as the best internationally,” she said.

Kaminski suggested Penn State’s turfgrass science program is so respected because of its close relationship with so many golf course managers around the world — many who are alumni of the program. Penn State focuses on what the industry needs, he pointed out, and this recent research is a good example.

“Our study is the first to directly compare a broad range of DMI fungicides on both annual bluegrass and creeping bentgrass,” he said. “We focused on real-world application scenarios to make the findings immediately useful to superintendents. The results help clarify which products are more likely to cause phytotoxicity on specific species and under what circumstances, providing actionable guidance for choosing safer options without sacrificing disease control.”

Turfgrass research at Penn State is rooted in solving practical challenges for golf course managers, Kaminski explained.

“Whether it’s improving fungicide strategies, identifying disease outbreaks or evaluating new technologies, our work is always focused on delivering solutions that make turf management more effective and sustainable,” he said.

The Paul R. Latshaw Graduate Fellowship partially supported this research.

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