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Issue link: http://gcmdigital.gcsaa.org/i/234582

CUTTING EDGE The research described in these summaries is funded in part by USGA. Teresa Carson Photo by Joseph A. Roberts Biostimulants and a PGR affect bentgrass etiolation Etiolation of creeping bentgrass has recently emerged as a signifcant problem on golf course greens. In 2011, feld and greenhouse trials were initiated to evaluate the impact of biostimulants and the plant growth regulator (PGR) trinexapac-ethyl on etiolation caused by Acidovorax avenae and Xant omonas translucens. Biostimulants (Astron, BioMax, CytoGro, Knife Plus, Nitrozyme, Perk Up) and trinexapac-ethyl were selected for study based on their frequency in etiolation samples submitted to the N.C. State University Turf Disease Clinic. Treatments applied at label rates were arranged as a split-plot, randomized complete-block design with biostimulants (14-day interval) as the main plot and trinexapac-ethyl (0, 7- and 14-day intervals) as the subplot. Etiolation developed naturally in fall 2011, and X. translucens was frequently isolated. In 2011, biostimulants did not infuence etiolation development; trinexapac-ethyl applied at 7- and 14-day intervals signifcantly reduced etiolation, regardless of the biostimulant. Etiolation was slow to develop in 2012 and 2013, so plots were inoculated with A. avenae. In summer 2012 and 2013, biostimulants did not signifcantly affect etiolation; trinexapac-ethyl applied at 7- and 14-day intervals signifcantly increased etiolation regardless of the biostimulant. Greenhouse trials are ongoing to evaluate the impact of biostimulant and PGRs on etio- 150 GOLF COURSE MANAGEMENT 01.14 lation. — Joseph A. Roberts (jarober3@ncsu.edu) and David Ritchie, North Carolina State University, Raleigh, N.C. feet/14 days). Potassium carbonate and potassium nitrate were applied at an N:K ratio of 1:1. A no-potassium control was included in the trial, as was a no-nitrogen control, with potassium chloride applied at the same potassium rate as the 1:1 treatments. Treatments were applied biweekly along with nitrogen as urea (0.1 pound N/1,000 square feet; excluding the no-nitrogen control and potassium nitrate treatment) April 24−Nov. 10, 2012, and April 23−Nov. 1, 2013. In both years, treatments receiving both nitrogen and potassium had signifcantly less anthracnose than either nutrient alone, regardless of potassium source and rate. In 2012, few differences were seen between potassium sources and rates; by Aug. 6, 2013, greater rates of potassium (1:1 and 2:1) had signifcantly less disease than the lowest potassium rate (4:1). Potassium fertilization alone (no nitrogen) had signifcantly less disease than nitrogen fertilization alone by the end of 2012 and through most of 2013. Soil and leaf tissue samples will be used to de- Photo by Charles J. Schmid Potassium affects anthracnose The objective of this two-year feld study was to determine the effect of potassium source and rate on anthracnose severity of Poa annua putting green turf. Potassium sulfate and potassium chloride were applied at N:K elemental ratios of 1:1, 2:1 and 4:1 (equivalent to 0.33, 0.17 and 0.08 pound K 2O/1,000 square termine suffciency levels for potassium relative to anthracnose severity. — Charles J. Schmid; Bruce B. Clarke, Ph.D. (clarke@aesop.rutgers.edu); and James A. Murphy, Ph.D., Rutgers University, New Brunswick, N.J. Teresa Carson (tcarson@gcsaa.org) is GCM's science editor.

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