By Paul Koch, University of Wisconsin – Madison
As the calendar turns to October and the leaves begin to change, the conversation among golf course superintendents in the northern US (and similar climates worldwide) inevitably turns towards buttoning up the course for the season. An important part of that buttoning up process is applying snow mold fungicides, and what used to be a fairly straightforward timing of applying products has become more complicated in recent years. Overall warmer fall conditions, of which this year looks to be a great example, may mean later applications will be more effective. But waiting until the last minute increases the risk that you don’t get the app out at all, with potentially devastating consequences.
All this begs the question, what is the best time to apply snow mold fungicides? As you might guess there’s a lot that goes into answering that question, but ideally, we would use a data-driven approach to optimize the application timing of our snow mold fungicides. For the last 9 years my program at Wisconsin has been working on a model that uses the environmental conditions each fall to tell you when the best time is to spray for snow mold. We have been testing this model at locations in Madison (southern Wisconsin), Wausau (central Wisconsin), and Minocqua (northern Wisconsin) by spraying a fungicide one time during the fall at 2-week intervals until it snows, then rating the amount of snow mold that occurs with each timing the next spring.
So, what have we learned in 9 years of research? First, application timing matters a lot. In one example from Minocqua, a gap of just 12 days was the difference in either excellent control or basically zero control (Figure 1). The difference in control in this situation was likely due to the snow mold fungi ‘waking up’ between the first date and the second date, allowing the fungus to absorb the fungicide and be killed back after the later application date. Second, making your final application 2-3 weeks ahead of permanent snow cover provides the best timing in the majority of situations. For example, we didn’t see significant increases in control if you sprayed the day before it snowed or 2 weeks before it snowed. It appears there is a window of optimal snow mold control, and our hope is that our model will be able to tell you exactly when that window is open for business in your location. We will be field-testing this model again this winter and hope to be able to release the final version in the next 1-2 years.
If you have any questions about this research or your snow mold fungicide application timing reach out to me by email at [email protected].