Influence of Plant Growth Regulators and Mowing on Two Bermudagrasses

‘Tifway‘ hybrid bermudagrass [Cynodon transvaalensis Burtt-Davy × C. daetylon (L.) Pers.] and common bermudagrass [C. dactylon (L.) Pers.] are popular turfgrasses used throughout the southern USA. When both grasses are manageda s a medium- to high-quality turf, frequent mowings are needed to limit vegetative growth and seedhead emergence. Plant growth regulators offer the potential to reduce the number of mowings needed by bermudagrass. Therefore, experiments were conducted on Tifway and common bermudagrasses to determine the effects of plant growth regulators on vegetative growth, seedhead suppression, and mowing requirements. Flurprimidol {α-(1-methylethyl)-α-[4-(trifluoro-methoxy) phenyl]-5-pyrimidine-methanol}, paclobutrazol, {(±)-(R*R*)β-[(4-chlorophenyl) methyl]-α-(1,1-dimethylethyl)-lH-1,2,4-triazole-l-ethanol}, and trinexapac-ethyl [4(cyclopropyl-α-hydroxy-methylene)-3,5-dioxocyclohexanecarboxylic acid ethyl ester] plant growth regulators were each applied at various rates in three applications at 4-wk intervals. When Tifway bermudagrass was treated initially with trinexapac-ethyl at 0.2 kg ha⁻¹, and followed by 0.1 kg ha⁻¹ at 4 and 8 wk, vegetative growth and seedheads were suppressed for 12 wk and the number of mowings were reduced by 70 and 67% during 1992 and 1993, respectively. However, the quality of Tifway bermudagrasws as significantly lowered in plots treated with trinexapac-ethyl at this rate at four rating dates during 1992 and three rating dates during 1993, when compared with turfgrass treated initially at 0ol kg ha⁻¹, and followed by 0.05 kg ha⁻¹ at 4 and 8 wk. Commobne rmudagrassw as less affected by these treatments. Neither flurprimidol nor paclobutrazol applied in three applications during a 12-wk period provided consistent vegetative growth and seedhead suppression of common bermudagrass during 1992 and 1993. Contribution from the Georgia Agricultural Experiment Station supplied by hatch and state funds.