Golf Course Management

JUN 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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06.18 GOLF COURSE MANAGEMENT 71 and growth above 1 cm (0.4 inch) was har- vested every seven, 14, 21 and 28 days. Pooled across all six grasses, the three low - est nitrogen treatments decreased weekly clip- ping production 17% to 29%, whereas the three highest nitrogen treatments sustained clipping production. e direct application of these results for putting green management is not clear because of the differences between plant culture in a greenhouse and that in the field. It is also expected that ultradwarf ber - mudagrasses maintained at 1 cm in a green- house would perform differently than plants maintained at putting green mowing heights. is was the first research on responses of off- type ultradwarfs to nitrogen applications, and field research should be carried out to support the results of this experiment. In a separate experiment, trinexapac-ethyl (Primo MAXX, Syngenta) was applied to the same off-type grasses and ultradwarf culti - vars in the greenhouse at 0, 0.1875, 0.375, 0.75, 1.5, 3, 6 or 12 fluid ounces/acre (13.7, 27.4, 54.8, 109.6, 219.2, 438.5 or 876.9 ml/ hectare). On each date that significant differ - ences were detected, mean clipping weights following application at 3 fluid ounces/acre were not significantly different from mean clipping weights following application at 6 or 12 fluid ounces/acre. ese results suggest that, under the conditions of our experiment, there was not a benefit to applying rates greater than 3 fluid ounces/acre in a single application; however, field validation of this response is warranted. Pooled across all Primo MAXX rates, the six grasses responded differently. Mean clip - ping weight for the off-type grass in cluster one (OTC1) was 21% to 27% greater than mean clipping weights for Champion, MiniVerde and off-types in clusters two and three. OTC1 (longer internode length) produced 15% more clippings than TifEagle in this experiment; however, this response was not statistically sig - nificant. e three off-type grasses and three commercial cultivars used in this experiment were genetically similar but exhibited differ - ential responses to trinexapac-ethyl. Off-type grasses present in putting greens that are simi - lar to OTC1 have the potential to disrupt the functional and aesthetic characteristics due to differential susceptibility to trinexapac-ethyl. What can be done? Regardless of the origin, morphology or ge- netics, off-type grasses continue to be an issue in ultradwarf putting greens. e manage - ment of putting greens with off-type grasses is still a "known unknown," although we have researched a few beginning guidelines to help mitigate their presence. e goal of managing these ultradwarf putting greens is to balance the growth of the desirable cultivar and the off-type. at being said, adjusting nitrogen application and PGR application programs (for example, trinexapac-ethyl) is critically im - portant on ultradwarf putting greens with off- type grasses. Certain off-type grasses are less regulated by trinexapac-ethyl than desirable ultradwarf cultivars, and frequent applications (every three to seven days) at high rates (that is, > 3 fluid ounces/acre) can lead to severe growth suppression of the ultradwarf cultivar, whereas the off-type grass can still be actively growing. It is important to maintain consis - tent growth among morphologically different Multidimensional scaling plot Figure 4. Multidimensional scaling plot (MDS) of nucleotide variants from 55 samples represented by black and colored dots: 47 off-type and desirable ultradwarf bermudagrasses sampled from golf course putting greens; six hybrid bermu - dagrass cultivars (Champion, MiniVerde, Tifdwarf, TifEagle, Tifgreen and Tifway); and two progenitor species (Cynodon dactylon and C. transvaalensis). The small box within the graph denotes the region where the majority (32) of off-type and desirable samples from golf course putting greens and ultradwarf cultivars are clustered. Samples in this region are considered genetically similar. 0.10 0.05 0.00 -0.05 -0.10 -0.15 -0.20 -0.1 0.0 0.1 0.2 0.3 0.4 MDS component 2 MDS component 1 * * CH DB DA MV S TA TB TD TE TG TW

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