Suppression of a Perennial Subspecies of Annual Bluegrass (Poa annua spp. reptans) in a Creeping Bentgrass (Agrostis stolonifera) Green with Plant Growth Regulators

TLDR: Flurprimidol applied in three spring and three fall applications did not suppress the perennial subspecies as effectively as paclobutrazol and neither chemical injured creeping bentgrass greater than 20% in the spring.

Abstract: Paclobutrazol and flurprimidol were evaluated for suppression of a perennial subspecies of annual bluegrass in a creeping bentgrass green. Three applications of paclobutrazol in the spring (Mar. 17, Apr. 17, and May 17) followed by three applications in the fall (Oct. 2, Nov. 2, and Nov. 30) suppressed the perennial subspecies ≥ 72% at 3 wk after the final treatment. However, suppression was reduced to ≤ 57% by 4 mo after the final fall application. Flurprimidol applied in three spring and three fall applications did not suppress the perennial subspecies as effectively as paclobutrazol. Suppression was ≤ 47% at 3 wk after the final flurprimidol treatment and was only ≤ 20% by mid-March. Neither chemical injured creeping bentgrass greater than 20% in the spring. However, leaf discoloration injury from the initial October application ranged from 26 to 30% for paclobutrazol in 1993 and 21 to 28% for flurprimidol in 1994. When injury occurred in October it was temporary and the creeping bentgrass recovered within 3 to 4 wk. Paclobutrazol and flurprimidol applied in November did not injure creeping bentgrass. Nomenclature: Flurprimidol, α-( 1 -methylethyl)-α-[4-(trifluoromethoxy)phenyl]-5-pyrimidine-methanol; paclobutrazol, (±)-(R * R * ) β-[(4-chlorophenyl)methyl]-α-(1,1-dimethylethyl)-1H-1,2- 4-triazole- 1-ethanol; Poa annua spp. reptans (Hausskn.) Timm. # 3 POAAN; creeping bentgrass, Agrostis stolonifera L. 'Penncross.'