Turf update: Do I need to reapply snow mold fungicides?

The mild winter weather has resulted in the possibility of new snow mold outbreaks and the need for golf course superintendents to reapply fungicides.

Patches of discolored turf on a putting green caused by snow mold.
Snow mold on a putting green. Photo by Kevin Frank, MSU.

The lack of winter weather is causing much discussion on the efficacy of snow mold fungicides applied in December. Snow mold fungicides applied in December were likely broken down by mild temperatures, rain and snow melt but that doesn’t necessarily mean we will see severe snow mold outbreaks when spring arrives. I recently visited with Paul Koch, University of Wisconsin, on whether he recommends reapplying fungicides at this time. Koch, being a true academic, responded with, “It depends.”

It depends on what the weather brings us for the rest of winter. Koch is confident that fungicides applied in November and December are gone but they were effective in reducing fungal populations. At this time, previously treated areas are still mostly free of snow mold. It’s what happens next that’s important.

Koch emphasized, “If we get some cold temperatures before getting more snow that froze the ground up, then the risk for further snow mold development is low and a reapplication likely wouldn't be necessary. However, if we stay mild and unfrozen and a large snow falls on the unfrozen ground, there could be LOTS of snow mold that develops.”

Ultimately, once again it appears we are at the whim of Mother Nature and the weather forecasters in trying to assess how much risk there is for further snow mold outbreaks. I asked Koch if he recommended golf course superintendents make an additional fungicide application at this time. He responded with, “For those in the southern half of lower Michigan where snow mold pressure is much lower, I would lean against reapplying. But in northern Michigan and the Upper Peninsula where the likelihood is higher that winter will return at some point, a reapplication may be more warranted.”

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