Golf Course Management

AUG 2018

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

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08.18 GOLF COURSE MANAGEMENT 71 CUTTING EDGE Teresa Carson Pythium patch of annual bluegrass In 2005, a new disease of annual bluegrass potentially caused by various Pythium species was observed on golf course putting greens in the northeastern United States. e disease primarily appears to impact annual bluegrass grown on native soil putting greens within mixed stands of creeping bentgrass. Although several cases of this foliar disease have been ob - served since the initial observation, the wide- spread appearance of symptoms characteristic of the disease appeared on 13 golf courses in 2016. Symptoms on annual bluegrass include yellow-to-orange circular patches ranging from a few inches to more than a foot in diam - eter. Disease symptoms are similar to those of summer patch, with creeping bentgrass gener - ally filling in voids following the death of the annual bluegrass. Following incubation, coe - nocytic mycelium can be observed in the can- opy of symptomatic leaves. Individual leaves look discolored and/or water-soaked and even - tually collapse. Initial findings suggest that a complex of Pythium species may be the cause of this purported new disease that has been re - ferred to as Pythium patch. Research is being conducted at Penn State to investigate the causal agent(s) of this potential new disease and to determine management options for golf course superintendents. e objectives of this study are to: identify potential pathogenic species associated with Pythium patch symp - toms, identify various biological aspects of the organisms involved, and identify cultural and chemical management options. — John E. Ka- minski, Ph.D. (kaminski@psu.edu), and Patrizia Rollo, Penn State University, University Park, Pa. DLI requirement of a creeping bentgrass green affected by shade intensity and timing Shade decreases photosynthetically active radiation (PAR), which limits turfgrass qual - ity. e daily light integral (DLI) is the cu- mulative PAR for one day at a given site and has been shown to estimate the light require - ments of various turfgrass systems effectively. However, the minimum DLI necessary to produce acceptable quality on a creeping bentgrass putting green has yet to be deter - mined. is research aimed to determine the DLI requirement of a creeping bentgrass green by evaluating the effects of shade in - tensity and timing. In addition, this study evaluated how applications of Primo Maxx (trinexapac-ethyl), a plant growth regulator known to increase shade tolerance, and Turf Screen, a turfgrass colorant marketed to in - crease photosynthetic efficiency, could influ- ence minimum DLI requirements. Four dif- ferent shade-intensity treatments (0%, 70%, 80% and 90% shade) were applied to the turf in morning (sunrise to solar noon) or after - noon (solar noon to sunset) to observe dif- ferences in turf quality from May through October in 2016 and 2017. Quantum light sensors measuring cumulative PAR under each shade level were used to determine the DLI for each treatment. After two years of shade treatments and quality evaluations, it was determined that the minimum DLI requirement for a Tyee creeping bentgrass green is 30 mol/square meter/day. Afternoon shade was more detrimental to turf health than morning shade in 2016, but there was no shade timing effect in 2017. Although Primo Maxx and Turf Screen improved turf quality on late-summer rating dates, they did not significantly reduce the minimum DLI requirement of creeping bentgrass. — Travis R. Russell, Douglas E. Karcher, Ph.D. (karcher@ uark.edu), and Michael D. Richardson, Ph.D., Uni - versity of Arkansas, Fayetteville Earlier versions of these summaries were published in the 2017 ASA-CSSA-SSSA Meeting Abstracts, ASA, CSSA and SSSA, Madison, Wis. Teresa Carson (tcarson@gcsaa.org) is GCM 's science editor. Photo by Travis Russell Photo by John Kaminski

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