Golf Course Management

FEB 2019

Golf Course Management magazine is dedicated to advancing the golf course superintendent profession and helping GCSAA members achieve career success.

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66 GOLF COURSE MANAGEMENT 02.19 Kurt Hockemeyer Paul Koch, Ph.D. Plant uptake and optimal timing of snow mold fungicides Current results indicate that application timing of snow mold fungicides has a significant effect on fungicide efficacy. Collectively known as snow molds, Typh- ula blight and Microdochium patch are the primary low-temperature diseases of turf - grass around the world (2, 5). Typhula blight (causal agents are Typhula incarnata or T. ishikariensis) requires snow cover in excess of 60 days to develop and was ranked the second- most important turfgrass disease in a 1996 Golf Course Superintendents Association of America (GCSAA) survey of golf course su - perintendents from the Great Lakes region (5). Microdochium patch (the causal agent is Microdochium nivale) does not require snow cover to cause disease, though it is most severe under prolonged snow cover and is often ob - served in the same stand as Typhula blight (6). Traditional fungicide timing Control of snow molds has traditionally been obtained with one or two fungicide ap - plications in the fall shortly before snow cover. However, timing of these fungicide applica - tions has been the source of considerable de- bate among superintendents in recent years. Some superintendents make their applications as close to snow cover as possible, thereby minimizing fungicide degradation before winter. is timing is supported by recent re - search completed at the University of Wiscon- sin, and funded by the GCSAA, that indicates rainfall events and temperatures over 40 F (4.4 C) can rapidly deplete foliar concentra- tions of both iprodione and chlorothalonil during the winter months (4). However, tim - ing the application so close to snow cover may increase risk for environmental contamination if the fungicides are applied to frozen soils. is timing also increases the chances that an unforeseen snowfall will occur before the fun - gicides can be applied. More recently, concern has been voiced about the potential for re - duced fungicide uptake — and hence reduced protection from disease — of plant-penetrant snow mold fungicides (such as propiconazole) when the turf is not actively growing. Concerned about these issues, other super - intendents apply their snow mold fungicides well in advance of the typical onset of snow cover. However, the risk for fungicide deg - radation before snow cover is significant if rainfall and/or warm temperatures occur, and there is limited research indicating that low temperatures and low plant activity impact fungicide uptake. Despite the importance and lack of clar - ity surrounding the application timing and uptake of snow mold fungicide, relatively lit - tle research has been published on the topic. Research published in 2013 (1) did not see a significant increase in Typhula blight con - trol when a second fungicide application was made one month before snow cover. On the other hand, more recent research (3) found an 80% reduction in Typhula blight (relative to the non-treated control) when only an "early" This research was funded in part by a grant to GCSAA from the Environmental Institute for Golf. Poor snow mold control can be damaging and impact playability in spring. Photos by Paul Koch

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