Verdure: Rolling for optimum ultradwarf bermudagrass

What's the best combination of trinexapac-ethyl and lightweight rolling for maximum ball roll on ultradwarf bermuda greens? 


This month’s Verdure column may remind us of the lyrics to Frankie Lane’s famous Western theme song “… Rollin’, rollin’, rollin’, keep them dawwgies rollin’, RAW-HIDE!”  

Rolling has become commonly accepted for managing premium putting green surfaces. Lightweight rolling of putting greens is implemented to complement or replace daily mowing, along with the goal of sustaining or improving surface playing conditions. This type of rolling practice is associated with increased golf ball roll distance. The “Doctor of Green Speed” — Thom Nikolai, Ph.D., of Michigan State University (East Lansing) — has written extensively on the topic: “The Superintendent’s Guide to Controlling Putting Green Speed.”

The purpose of plant growth regulator applications to putting greens is to reduce rapid shoot growth, effectively manage clippings and contribute to the production of a smooth and consistent putting surface that also is favorable for ball roll distance. Plant growth regulators are often routinely applied to ultradrawf bermudagrass (Cynodon dactylon [L.] Pers. × C. transvaalensis Burtt-Davy) putting greens, along with rolling practices, too.

Research was conducted on ultradwarf bermudagrass putting greens to determine if ball roll distance could be influenced by various application rates of a trinexapac-ethyl plant growth regulator combined with lightweight rolling. In other words, can we “dial-in” an optimum application rate of trinexapac-ethyl along with lightweight rolling to maximize ball roll distance on this putting green species?

Field studies were conducted on MiniVerde ultradwarf bermudagrass at the University of Tennessee (Knoxville) and at Mississippi State University (Starkville). Putting greens at both sites were constructed of a USGA-specification sand root zone and mowed at 0.125-inch (3.2 millimeters) height-of-cut. The bermudagrass at both sites was treated with fungicides to prevent disease along with routine maintenance of fertilizers, irrigation and sand topdressing every two weeks during the growing season.

At both locations, test plots measured 4 feet by 16 feet (1.2 meters by 4.9 meters) arranged as strip-plots, meaning those entire plots were each treated with trinexapac-ethyl at three application rates. Those whole plots were further divided into sub-plots, with lightweight rolling conducted at none or five times per week. Trinexapac-ethyl (Primo MAXX; Syngenta) was applied weekly at 1, 3 or 9 fluid ounces per acre (70, 210 or 630 milliliters per hectare), and rolling was achieved with a Greens Roller (RB48-11A; Tru-Turf). All treatment combinations of trinexapac-ethyl and lightweight rolling were replicated three times. Trinexapac-ethyl applications and rolling occurred May through August at the Tennessee site, and June through September at the Mississippi site.

At both locations, ball roll distance was measured on each test plot after 3 p.m. and three times per week for 40 measurements total at each site. The Pelzmeter was used at the Tennessee site, and the Stimpmeter was used at the Mississippi site. With both devices, three golf balls were rolled in opposite directions lengthwise and the distance measured and averaged. Of note, ball roll distance data from the Pelz­meter and Stimpmeter were highly correlated.

What did these two field studies reveal? Overall, trinexapac-ethyl applications at 3 fluid ounces per acre combined with lightweight rolling five times per week produced a similar ball roll distance compared to applying 9 fluid ounces per acre trinexapac-ethyl without the rolling. Ball roll distance in plots treated with 3 fluid ounces per acre trinexapac-ethyl combined with lightweight rolling was only 5 inches (12.5 centimeters) less than plots treated with only 9 fluid ounces per acre trinexapac-ethyl. The researchers concluded this difference would be “imperceptible to golfers.”

Also, in both field studies, 3 fluid ounces per acre trinexapac-ethyl was associated with better overall bermudagrass visual quality. The researchers conducting these studies also suggested that these plant growth regulator applications could be timed according to air-temperature-based growing degree day models.

Overall, weekly trinexapac-ethyl applications along with lightweight rolling increased ball roll distance on the MiniVerde bermuda­grass putting greens in this study. When it comes to rolling putting greens, if Frankie Lane is not to your taste, perhaps The Doors’ lyrics also fit: “Keep your eyes on the road, your hand upon the wheel … let it roll, baby, roll.”

Source:  Reasor, E.H., and J.T. Brosnan. 2020. Trinexapac-ethyl applications and lightweight rolling on ultradwarf bermudagrass putting greens. Crop, Forage & Turfgrass Management 6:e20036 (

Mike Fidanza, Ph.D., is a professor of plant and soil science in the Division of Science, Berks Campus, at Pennsylvania State University in Reading, Pa. He is a 22-year member of GCSAA.