Golf Course Management

JUN 2013

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

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Research in progress Photo by M. Schiavon Primo on warm-season turf Plant growth regulators (PGR) and soil surfactants are purported to reduce turfgrass irrigation needs without a loss in quality. A study was conducted at New Mexico State University in Las Cruces, N.M., in 2010 and 2011 to determine turf quality and drought stress of Princess 77 bermudagrass and Sea Spray seashore paspalum treated with either a soil surfactant (Revolution) or a PGR (Primo Maxx). Irrigation was applied daily at 50% ETo from either a sprinkler or a subsurface-drip system with either saline (TDS = 1,600 ppm) or potable (500 ppm) water. Normalized Difference Vegetation Indices (NDVI) and visual ratings were collected twice monthly from June to November to assess turf stress and quality. Chlorophyll a and b and carotenoid content were measured monthly during the summer to determine whether pigment content was associated with resistance to environmental stresses. Primo Maxx increased turf quality and chlorophyll and carotenoid content in summer and enhanced fall color retention. Sprinkler-irrigated plots had higher turf quality in summer. Saline irrigation water decreased turf quality of Sea Spray treated with Revolution. Princess 77 treated with Primo had higher quality than the control when irrigated with saline water but lower quality than plots irrigated with potable water. No correlation was found between chlorophyll content and either NDVI or visual quality. — Marco Schiavon, Ph.D.; Bernd Leinauer, Ph.D. (leinauer@nmsu.edu); and Matteo Serena, New Mexico State University, Las Cruces, N.M. Suppressing annual bluegrass in greens Annual bluegrass (ABG) invades creeping bentgrass (CBG) putting greens, reducing uniformity and increasing maintenance costs. To control ABG, superintendents may use a root-absorbed plant growth regulator (PGR) such as Cutless MEC (furprimidol) and/or fertility sources and nitrogen. This two-year feld study evaluated the potential infuence of Cutless MEC (24.6 fuid ounces/acre/14 days) and two liquid fertilizer sources (urea vs. balanced-complete) applied at two rates (6.5 vs. 13.1 pounds/acre/14 days) on a native-soil research green during the growing seasons. After two years, treatments containing Cutless MEC decreased ABG from the ~30% initial levels to ~4%-10%. Where Cutless MEC was not applied, fertilizer source and rate had signifcant effects. When urea was applied at either nitrogen rate, ABG populations decreased ~25%. The low rate of the balanced-complete fertilizer resulted in no change; the high rate stimulated ABG by 84%. Regularly applying a root-absorbed PGR successfully suppresses ABG, but applying a balanced complete fertilizer at the study rate may increase ABG encroachment. — William T. Tudor Jr.; Cale Big- cutting edge Photo by W.T. Tudor elow, Ph.D. (cbigelo1@purdue.edu); James Camberato, Ph.D., Purdue University, West Lafayette, Ind.; and B. Todd Bunnell, ValleyCrest Golf, Carmel, Ind. Do strobilurins reduce stress in bentgrass greens? Research trials were initiated in Strawberry Plains, Tenn., and Florence, S.C., to evaluate the plant health benefts of strobilurin fungicide applications on creeping bentgrass greens. Both locations received applications of Insignia SC (pyraclostrobin, 7.85 ounces/acre), Heritage TL (azoxystrobin, 8.7 ounces/acre) and Disarm (fuoxastrobin, 7.85 ounces/acre). Visual turfgrass quality, Normalized Difference Vegetation Index (NDVI), Digital Image Analysis (DIA) and disease severity were rated at all locations. Soil profles were removed two weeks after the second strobilurin application to assess total root length and density using scanning software. In South Carolina, pyraclostrobin-treated plots had signifcantly greater NDVI compared to the other fungicide treatments on fve rating dates in July and August. This same result was not observed in Tennessee. To get the full benefts of strobilurin fungicides, superintendents should apply them during disease activity. Strobilurin fungicides may promote plant health during summer stress, but these effects may depend on a number of unknown factors. — Jesse J. Benelli; Brandon Horvath, Ph.D.; Jim Photo by David Shell Brosnan, Ph.D.; and Dean Kopsell, Ph.D., University of Tennessee, Knoxville, Tenn.; and S. Bruce Martin, Ph.D., Clemson University, Florence, S.C. GCM Teresa Carson (tcarson@gcsaa.org) is GCM's science editor. Teresa Carson June 2013 GCM 89

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