Efficacy of Plant Growth Regulators for the Removal of Annual Bluegrass from a Creeping Bentgrass Putting Green.

Annual bluegrass (Poa annua: ABG) is an undesirable and invasive plant in creeping bentgrass (Agrostis stolonifera: CBG) putting greens; thus, ABG suppression is an important turf management practice for some turf areas. Common plant growth regulators (PGR’s) used in turfgrass maintenance alter gibberellic acid (GA) production and accumulation. This can alter shoot growth on putting green species which, in previous studies, has shown to suppress ABG growth more than CBG allowing CBG to grow more laterally into suppressed ABG areas. A field study was conducted in 2016 at the Hancock Turfgrass Research Center in East Lansing, MI. to evaluated the efficacy of trinexapac-ethyl, flurprimidol, paclobutrazol and combinations of those three chemicals on the suppression of ABG evaluating plant health effects on a CBG putting green. Relative chlorophyll content, visual turfgrass quality, percent annual bluegrass cover, plot shoot mass (clippings) and multispectral radiometry were measured. Results include the combination of trinexapac-ethyl with flurprimidol and paclobutrazol deceased annual bluegrass percentages greatest when compared to the untreated control while also decreasing total clipping weights collected.  Trinexapac-ethyl with flurprimidol and paclobutrazol and trinexapac-ethyl with flurprimidol had better turfgrass quality when compared to the untreated control. Combination of GA inhibiting PGR’s were found to be effective at decreasing the amount of annual bluegrass within a bentgrass putting green and decreasing the amount of shoot growth while increasing turf color reflectance. Results from this experiment suggest that by applying combinations of GA altering PGR’s, ABG suppression can occur resulting in a more uniform CBG putting green.  Applying these types of PGR’s also improved the quality, turf color reflectance, and relative chlorophyll content of CBG when compared to an untreated control.