EFFECT OF PACLOBUTRAZOL AND FLURPRIMIDOL ON SUPPRESSION OF POA-ANNUA SPP REPTANS IN CREEPING BENTGRASS (AGROSTIS-STOLONIFERA) GREENS

Plant growth regulators paclobutrazol and flurprimidol were evaluated for suppression of Poa annua spp. reptans, a perennial biotype of annu al bluegrass, in a creeping bentgrass green. Paclobutrazol at 0.6 kg a i/ha applied on Mar. 15, followed by 0.3 kg/ha on Apr. 29, 0.6 kg/ha o n Oct. 1, and 0.3 kg/ha on Nov. 12 for each of 2 yr suppressed P. annu a spp. reptans 28% approximately 4 mo after the final treatment. When paclobutrazol was applied at 0.3 kg/ha in each of four applications du ring the same period, suppression was similar to that with the higher rate 1 and 2 mo after final treatment but declined to 7% by 4 mo. Supp ression of P. annua spp. reptans from flurprimidol applied four times during each of 2 yr was 22 to 27% 1 mo after final treatment but no su ppression was noted 2 mo after the final treatment. Maximum creeping b entgrass injury was less than 20% when either paclobutrazol or flurpri midol was applied in the spring. However, creeping bentgrass injury wa s approximately 30% in the fall when either chemical was applied in th e spring and repeated in October at 0.6 kg/ha.