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B. Jack Johnson

A field study was conducted to assess the effects of N and Fe with trinexapac-ethyl (TE) on established `Tifway' bermudagrass (Cynodon dactylon × C. transvaalensis) during 2 years at Griffin, Ga. There were no TE × Fe or N treatment interactions when applied in three applications at 4-week intervals each year. Combinations of Fe with TE improved turfgrass quality over TE alone at 1 to 2 weeks after each treatment. The improvement from Fe sources was 17 % higher with Sprint 300 and SoluPlex, 33% higher with Ferromec and LawnPlex, and 67% higher with ferrous sulfate. Vegetative suppression of `Tifway' bermudagrass at 14 weeks after treatment ranged from 46% in 1994 to 28% in 1995 when treated with TE at 0.1 kg·ha-1 in three applications at 4-week intervals. Neither N or Fe influenced vegetative growth when applied with TE. Chemical name used: 4 (cyclopropyl-α-hydroxy-methylene)-3.5-dioxocyclohexanecarboxlic acid ethyl ester (trinexapac-ethyl).

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B.J. Johnson

A field experiment was conducted for 2 years to determine the effects of rate and time interval for repeated applications of the plant growth regulators (PGR) flurprimidol and paclobutrazol on vegetative suppression of `Tifway' bermudagrass [Cynodon transvaalensis Burtt-Davy × C. dactylon (L.) Pers.]. Suppression of vegetative growth of this grass was generally the same when either flurprimidol or paclobutrazol was applied twice after a 2-, 3-, or 4-week interval. The duration of growth suppression was also similar after initial application with flurprimidol at 0.84 kg·ha-l and repeated at 0.28 to 0.84 kg·ha-1 or with paclobutrazol applied initially at 1.1 kg·ha-1 an d repeated at 0.56 to 1.1 kg·ha-1. Both PGRs caused slight to moderate turfgrass injury at these rates, but the injury was temporary and the grass had fully recovered by 10 weeks. Chemical names used: α -(1-methylethyl)- α -[4-(trifluoromethoxy)-phenyl]-5-pyrimidinemethanol (flurprimidol); (±)-(R*R*) β -[(4-chlorophenyl)-methyl]- α -(1,1-dimethylethyl)-1H-1,2,4-triazole-l-ethanol (paclobutrazol).

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B.J. Johnson

A field experiment was conducted over 2 years to determine the effects of treatment dates with plant growth regulators (PGRs) on performance of `Tifway' bermudagrass [Cynodon transvaalensis Burtt-Davy] × [C. dactylon (L.) Pers.]. For flurprimidol at 0.84 kg·ha-1, the highest injury occurred from 16 or 28 June application in 1987 and from 17 May or June application in 1988. The injury was similar from treatment dates with flurprimidol + mefluidide or paclobutrazol + mefluidide. The PGRs were applied over a longer period in 1987 than 1988 without affecting vegetative suppression of `Tifway' bermudagrass. However, in 1988, the suppression from the 17 May treatment was equal to or better than that obtained when treatment dates were delayed until 1 June or later. Chemical names: α-(1 -methylethyl)- α -[4-(trifluoromethoxy)phenyl]-5-pyrimidinemethanol (flurprimidol); N -[2,4-dimethyl-5-[[(trifluoromethyl)sulfonyl]amino]phenyl]acetamide (mefluidide); (±)-(R*R*) β -[(4-chlorophenyl)-methyl]- α -(1,1-dimethylethyl)- 1H -1,2,4-triazole- 1-ethanol (paclobutrazol).

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J. Michael Goatley Jr., Victor L. Maddox, and Robert M. Watkins

Research was conducted over 2 years to evaluate efficacy of various levels and combinations of imazaquin and AC 263,222 for growth regulation of unimproved bahiagrass (`Pensacola') turf. Imazaquin at 0.42 kg·ha–1 caused only slight bahiagrass discoloration in all trials and reduced seedhead count (as compared to the nontreated control) by ≥80% for 8 weeks after treatment (WAT) following a July 1992 application. AC 263,222 at 0.042 or 0.056 kg·ha–1 applied in late May or June provided 100% seedhead control through 8 WAT. However, AC 263,222 applied in July 1992 and Aug. 1993 at 0.056 kg·ha–1 resulted in unacceptable discoloration through 8 WAT. AC 263,222 at 0.014 or 0.028 kg·ha–1 provided ≥90% seedhead control with only minimal discoloration following applications in July or Aug. 1993, indicating that lower rates of AC 263,222 provided acceptable seedhead control of bahiagrass during times when growth was slowed due to moisture stress. Chemical names used: (±)-2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-5-methyl-3-pyridinecarboxylic acid (AC 263,222); 2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-3-quinolinecarboxylic acid (imazaquin).