SEEDHEAD SUPPRESSION OF AN ANNUAL BLUEGRASS PUTTING GREEN

 

J. A. Borger, M. B. Naedel, and K. R. Hivner¹

 

Abstract

 

            Three separate annual bluegrass (Poa annua) seedhead suppression studies were conducted using various materials and application timings.  The first two studies, in 2009 and 2010, were conducted on a mature monostand of annual bluegrass at the Valentine Turfgrass Research Center, Penn State University, University Park, PA. The third study, conducted in 2011, was conducted on a ‘Pencross’ creeping bentgrass (Agrostis stolonifera) and annual bluegrass putting green at the Pennsylvania State University Blue Golf Course, University Park, PA.  The objective of the studies was to determine if selected materials could suppress seedhead formation of annual bluegrass under simulated golf course greens conditions.  All trials were randomized complete block designs with three replications each.  For the first study, treatments were applied on April 1 (EARLY), April 13 (BT), and May 6, 2009 (3 WABT).  For the second study, treatments were applied April 2 (EARLY), April 20 (BT), and May 5, 2010 (3 WABT).  For the third study, treatments were applied April 7 (EARLY), April 21 (BT), and May 12, 2011 (3 WABT). Treatments for all three trials were applied using a three foot CO₂ powered boom sprayer calibrated to deliver 80 gpa using one, flat fan, TP9508EVS nozzle at 40 psi.  The test areas at the Valentine Turfgrass research Center were maintained at 0.125 inch using a Toro triplex reel mower.  The test area at the Penn State Blue Golf Course was maintained at 0.140 inch using a Jacobsen walking reel mower.  Additionally, turfgrass was irrigated on an as needed basis to prevent moisture stress at both test sites.  The test sites consisted of approximately 65 percent annual bluegrass seedhead cover in the untreated test plots at the times of data collection.  Annual bluegrass seedhead cover was visually evaluated on May 6, 2009, May 17, 2010, and May 16, 2011, on a plot by plot basis.  Data for these studies were then transformed into a percent suppression value via an Abbott’s Transformation using Agricultural Research Manager software.  In the first study, Primo Maxx at 0.125 oz/M plus Proxy at 5 oz/M were evaluated alone or in combination with ProGibb T&O at 0.06 g ai/A at various timings.  All treated turfgrass revealed a significant level of seedhead suppression compared to that of untreated turfgrass, with the exception of Primo Maxx plus Proxy with a single application timed at boot stage (BT).  Turfgrass treated with Primo Maxx, Proxy, and ProGibb T&O applied EARLY and BT revealed significantly higher seedhead suppression than turfgrass treated with Primo Maxx plus Proxy applied once at BT.  In the second study, Primo Maxx at 0.125 oz/M plus Proxy at 5 oz/M were evaluated alone or in combination with ProGibb T&O at 0.06 g ai/A at various timings.  All treated turfgrass with the exception of ProGibb T&O at 0.06 g ai/A applied alone at any timing (except the EARLY timing) and Primo Maxx plus Proxy plus ProGibb T&O applied EARLY, did not significantly reduce the presence of annual bluegrass seedheads.  Notable results of this trial include a significant increase in seedhead suppression when Primo Maxx, Proxy, and ProGibb T&O were combined compared to Primo Maxx plus Proxy without ProGibb T&O applied EARLY or in succession (EARLY, BT). However, when these treatments were compared to one another with three total applications (EARLY, BT, and 3 WABT), no significant differences were found.  In the third study, Primo Maxx at 0.125 oz/M plus Proxy at 5 oz/M were evaluated alone or in combination with ProGibb T&O at 0.06 g ai/A at various timings.  All treated turfgrass, with the exception of ProGibb T&O applied alone three times (EARLY, BT, and 3 WABT), revealed a significant reduction of annual bluegrass seedhead cover when compared to untreated turfgrass.  When ProGibb T&O was added to Primo Maxx plus Proxy applied three times, a significant increase in annual bluegrass seedhead suppression was observed.  More research will continue to be conducted to investigate issues regarding the addition of gibberillic acid into annual bluegrass seedhead suppression strategies for golf course putting greens.

 

                                                                       

¹ Instructor, Research Technician II, and Research Technician I, Respectively, Department of Crop and Soil Sciences, Penn State University, University Park, Pa, 16802