With the emergence of glyphosate-tolerant cultivars, identifying management strategies not applicable with older cultivars need to be revisited. Objectives of these research trials were to quantify the growth regulation effects following a glyphosate application and to determine the safety of tank mixing glyphosate with another herbicide, various nitrogen (N) sources, and a plant growth regulator (PGR) on a glyphosate-tolerant perennial ryegrass [PRG (Lolium perenne L.)] cultivar, Replay. In the growth regulation trial, glyphosate was applied at 0 to 1.03 lb/acre, whereas PGRs flurpimidol, trinexapac-ethyl, paclobutrazol, and trinexapac-ethyl + flurpimidol were applied at 0.50, 0.18, 0.37, and 0.09 + 0.22 lb/acre, respectively, on 15 July 2010 and 2 Aug. 2012. In the tank mixing trial, dicamba (0.50 lb/acre), urea (15 lb/acre N), and ammonium sulfate [AMS (15 lb/acre N)] were applied alone or tank mixed with glyphosate at 0 to 0.52 lb/acre. Tank mixing urea with glyphosate had minimal effect on PRG color, while adding AMS consistently improved color at the highest glyphosate rate of 0.52 lb/acre. Twenty days following a glyphosate application, only rates >0.40 lb/acre resulted in significant growth regulation compared with untreated plots. This study indicates that tank mixing glyphosate with another herbicide, a PGR, and various N sources appear safe to the glyphosate-tolerant PRG cultivar. Also, the growth regulating effects of glyphosate applications would serve as an additional benefit to annual bluegrass (Poa annua L.) control reported in previous trials.
Plant growth regulator effects on winter hardiness of annual bluegrass putting green turf
