Reduced Herbicide Rates for the Control of Carpetgrass in Bermudagrass Putting Greens.

Common carpetgrass [Axonopus fissifolius (Raddi) Kuhlm.] is a stoloniferous, warm season perennial grass. Carpetgrass is adapted to soils that are commonly found in golf courses. Tolerance to low mowing height and limited labeled herbicides has increased the prevalence of carpetgrass in bermudagrass putting greens.

Experiments were conducted in Winder, GA to examine the control of carpetgrass in a hybrid bermudagrass putting green. The soil was an Appling sandy loam. Research was performed on a ‘Tifdwarf’ hybrid bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy] putting green (0.3 cm height). Treatments were applied to plots arranged in a randomized complete block design with three replications. Treatments included a non-treated check, foramsulfuron [Revolver] (0.06 kg ai ha^-1), MSMA (1.15 kg ai ha^-1), trifloxysulfuron [Monument] (0.01 kg ai ha^-1), nicosulfuron [Accent] (0.03 kg ai ha^-1), thiencarbazone + iodosulfuron + dicamba [Celsius] (0.13 kg ai ha^-1), and thiencarbazone + foramsulfuron + halosulfuron [Tribute Total] (0.08 kg ai ha^-1). Initial applications were conducted on 2 July 2012 and sequential applications were made 2 and 4 weeks later. Treatments were applied using a CO₂ pressurized backpack sprayer calibrated to deliver 375 L ha^-1 at 221 kPa.

Percent carpetgrass control for each treatment was calculated relative to initial carpetgrass cover. Analysis of variance was performed in SAS and means were separated according to Fisher’s protected LSD at the 0.05 significance level.

No bermudagrass phytotoxicity was observed throughout the length of the experiment. Tribute Total exhibited 68% carpetgrass control, 1 WAIT. All other treatments 1 WAIT resulted in ≤ 20% carpetgrass control. Tribute Total, Celsius, and MSMA (95%, 92%, and 77% control, respectively) outperformed Accent, Monument, and Revolver (47%, 43%, and 7% control, respectively) 5 WAIT. Carpetgrass control was greatest 10 WAIT. Tribute Total, Celsius, MSMA, Accent, Monument, and Revolver exhibited 100%, 100%, 93%, 92%, 53%, and 7% control, respectively, 10 WAIT. Research concludes that viable options are available for safe carpetgrass control in bermudagrass putting greens with sequential applications at low use rates.