SUPPRESSION OF A PERENNIAL SUBSPECIES OF ANNUAL BLUEGRASS (POA-ANNUA SPP REPTANS) IN A CREEPING BENTGRASS (AGROSTIS-STOLONIFERA) GREEN WITHPLANT-GROWTH REGULATORS

Paclobutrazol and flurprimidol were evaluated for suppression of a per ennial subspecies of annual bluegrass in a creeping bentgrass green. T hree applications of paclobutrazol in the spring (Mar. 17, Apr. 17, an d May 17) followed by three applications in the fall (Oct. 2, Nov. 2, and Nov. 30) suppressed the perennial subspecies greater than or equal to 72% at 3 wk after the final treatment. However, suppression was re duced to less than or equal to 57% by 4 mo after the final fall applic ation. Flurprimidol applied in three spring and three fall application s did not suppress the perennial subspecies as effectively as paclobut razol. Suppression was less than or equal to 47% at 3 wk after the fin al flurprimidol treatment and was only less than or equal to 20% by mi d-March. Neither chemical injured creeping bentgrass greater than 20% in the spring. However, leaf discoloration injury from the initial Oct ober application ranged from 26 to 30% for paclobutrazol in 1993 and 2 1 to 28% for flurprimidol in 1994. When injury occurred in October it was temporary and the creeping bentgrass recovered within 3 to 4 wk. P aclobutrazol and flurprimidol applied in November did not injure creep ing bentgrass.