Still severe — and often confounding

Courses in higher latitudes experienced the changing dynamics of snow mold during the winter of 2022-23.

University of Wisconsin associate professor Dr. Paul Koch observed divergent situations early in the season. Trial results in Michigan’s Upper Peninsula and northern Wisconsin demonstrated fungicide breakdown because of snow melt or rain following snow mold control applications. The situation proved different in northern Minnesota, where the snow fell atop snow and products worked as intended. Koch views the latter as an anomaly these days.

“We know if we have a warmup event, or a rainfall event, or snow melt event, the snow mold product, the fungicide, degrades relatively quickly,” he says. “Most products stay persistent on the turf throughout the winter if there’s not a rainfall or snow melt event … but there are very few locations where that happens anymore.”

Utah-based turfgrass researcher and consultant Adam Van Dyke encountered a contrasting scenario in the western Mountain states: snow arrived earlier than normal and never left. “Some courses got caught because they were unable to treat,” he says.

As winter becomes more unpredictable — January golf in Michigan, anyone? — tactics and solutions for controlling snow mold continue to evolve. Properly timing a snow mold application has become one of the most important late fall/early winter decisions facing a cool-weather superintendent. What somebody learned in school or on the job 30, 20 or even 10 years ago about application timing might not correlate to today’s conditions. “You just really have to go off historical record,” Van Dyke says, “but things have shifted somewhat since I started doing research. I think sprays are now a little bit later. For me, in my trials, it’s been right around Halloween the last 15 years. But this past year it was tight.”

Fall decisions impact the quality of playing surfaces in regions where golf seasons are revenue sprints with little margin for playability and aesthetic error. Before applying any snow mold control product, an understanding of what customers, members and bosses are willing to tolerate must be reached.

“Lately our winters are so different, I’m not even sure what the normal winter is anymore,” says Midwest-based Syngenta technical services manager Matt Giese, whose responsibilities include studying winter disease. “Taking the chance of making that application or not making that application is probably not something most superintendents would be willing to risk. What would happen if you didn’t do it? It could be a pretty significant recovery time in the spring along with everything else that goes on in the spring in terms of prepping the golf course for play.”

From Koch’s perspective, the type of snow mold pestering golf courses is a major transformation affecting control philosophies. Parts of the gray snow mold belt have recently turned into pink snow mold hotbeds. The shift means a superintendent’s late fall, winter and early spring alertness must be heightened.

“Snow mold isn’t getting less severe,” Koch says. “This past winter for a large part of the country was a great example of that, but what we are seeing is a shift toward more pink snow mold because it’s the more adaptable fungus to swings in conditions. Because it grows faster, it can adapt to a big warmup and a cooldown, where gray snow mold needs that consistent condition under the snow cover for a very long period of time.”

The shift also means superintendents must consider integrating multiple chemistries into control programs. Koch calls fludioxonil and iprodione “really strong chemistries against pink snow mold,” while DMIs demonstrate efficacy against gray snow mold. “That’s why it’s important to mix different chemistries together in your snow mold application, so you can fend off against multiple snow mold diseases,” he adds.

Control options recently expanded with the launch of a new versatile fungicide designed to control snow mold on golf courses: Tuque exoGEM from Syngenta. The combination includes fludioxonil and SOLATENOL technology (benzovindiflupyr). SOLATENOL is an SDHI found in Ascernity, a broad-spectrum fungicide launched in 2020. The new fungicide includes exoGEM, an advanced formulation offering greater uptake, distribution, rainfastness and retention.

Researchers in snow mold regions have tested and studied Tuque (pronounced tu:k) exoGEM under myriad conditions for multiple years.

“What we have learned about Tuque is that it’s a very strong pink snow mold product,” Koch says. “It has fludioxonil in there, which is probably the best single active ingredient against pink snow mold on the market. It has the SOLALETNOL in there that provides some control against gray snow mold as well. It has performed well in our trials over a number of years and over a number of sites. That’s what’s important for us as researchers. We want to see these products perform well across all of our locations over a number of years before we get comfortable making that recommendation. We have worked with Tuque long enough that we’re comfortable making that recommendation.”

The launch of Tuque exoGEM comes at an ideal time. The trifecta of heightened pink snow mold severity, restrictions on iprodione usage and increasing reports of fungicide resistance create a need for new solutions, according to Koch.

Van Dyke has conducted extensive work testing and observing Tuque exoGEM on cool-weather turf in the mountainous region he covers. “With different modes of action, this product will be important for superintendents to plug and play and learn which things work best for their course and the grasses that grow under the conditions that they have to deal with during winter,” he says. “It gives flexibility to develop and change programs as superintendents deal with an ever-changing environment and the pathogen environment that comes with it.”

Syngenta is guaranteeing as a 90-day option for snow mold control. Tuque exoGEM, according to its label, can be tank mixed with a fungicide from a different FRAC group for broader-spectrum activity and extended control.

“Tuque exoGEM by itself is going to be fantastic,” Giese says. “We have seen very good levels of control with Tuque exoGEM as a sole application. And there’s no reason you couldn’t tank mix it if you’re expecting more than 90 days of snow cover. You can tank mix it for longer levels of control with Banner Max II and Daconil brand fungicides. There are a lot of different tank mix combinations. For areas that have low-to-moderate snow cover, Tuque exoGEM is a really good option for snow mold applications.”

Giese recommends using Tuque exoGEM at the high label rate of 2.87 fluid ounces per 1,000 square feet for the most effective snow mold control.

Tuque is the Canadian word for a warm-knitted winter hat, and the fungicide is aptly named. The solution has the potential to hold multiple “hats” for superintendents beyond controlling snow mold.

“What’s different about Tuque exoGEM is that there is a plethora of other diseases that fall under the Tuque exoGEM umbrella,” says Giese, who adds that combining SOLATENOL and Medallion fungicide provides a strong combination against anthracnose.

Other common cool-season diseases listed on the Tuque exoGEM label include dollar spot, brown patch, summer patch and various types of leaf spot. Koch has studied Tuque exoGEM against dollar spot, the most prominent summer disease in the region where he works, and he says the formulation provides a “very solid 14-day product in our dollar spot trials.”

“Even when we have had a pretty high pressure, it’s done quite well,” Koch adds. “We have also tested it on bipolaris leaf spot and it performed well on our bipolaris leaf spot trial.”

Van Dyke has tested Tuque exoGEM on summer disease, although his summer work with the fungicide hasn’t been as abundant as his winter research. “This new product has shown excellent turf safety in the work that I have done on cool-season grasses,” he says. “That’s an important thing to know in the winter and warm summer.”

The environments where Van Dyke lives and conducts trials present contrasting research situations. He’s based in the Salt Lake City suburbs, where the elevation approaches 4,500 feet, yet the snow doesn’t stick around long enough for significant snow mold trial work. Less than an hour from his home, he studied a few sites that approached 200 days of snow cover during the winter of 2022-23.

The whims of winter mean snow mold will continue to yield research opportunities and control conundrums.

“You have to do your homework, read articles, talk to people who do the research, lean on your extension agents, talk to industry folks, because you really do just get one shot,” Van Dyke says. “If you’re doing this year over year, you learn what products work and you refine your timing. But Mother Nature is always throwing curveballs. Every year is a little bit different.”