Field studies were conducted in south Louisiana to identify plant growth regulators that suppress carpetgrass (Axonopus affinis Chase.) seedhead development. In an initial study, best results were obtained with sethoxydim (0.11 kg·ha-1) and sulfometuron methyl (0.6 kg·ha-1), which reduced seedhead development by 88% and 86%, respectively, compared to untreated plots 21 days after treatment. Sulfometuron methyl caused unacceptable carpetgrass injury, however. Evaluation of seven sethoxydim application levels between 0 and 0.34 kg a.i./ha showed that carpetgrass seedhead number and elongation rate declined with increasing sethoxydim amount [SEEDHEAD NUMBER (m-2) = 515 – 1340 (kg), R 2 = 0.82; ELONGATION (cm) = 25.3 – 151 (kg) + 276 (kg2), R 2 = 0.77]. Carpetgrass seedhead production was restricted up to 6 weeks after sethoxydim (0.17 and 0.22 kg·ha-1) application. Chemical names used: (2-[1-(ethoxyimino)butyl]-5-[2-ethylthio)propyl)-3-hydroxy-2-cyclohexen-1-one) (seth-oxydim); (2-[[[[(4,6-dimethyl-2-pyrimidinyl)amino]carbonyl]amino]sulfonyl]benzoic acid) (sulfometuron methyl).
Jack D. Fry and D. Wayne Wells
Billy J. Johnson
Two separate experiments (one and two applications and dates of treatment) were conducted on plant growth regulator (PGR) injury and seedhead suppression of centipedegrass [Eremochloa ophiuroides (Munro) Hack.]. Mefluidide caused less injury to centipedegrass than either imazethapyr or flurprimidol + mefluidide. Mefluidide applied at 0.56 kg·ha-1 in each of two applications at 2-week intervals suppressed seedheads of centipedegrass for 10 weeks. A single 0.56-kg·ha-1 application of the mefluidide failed to suppress seedheads when applied any time from mid-June until late July. A single treatment with flurprimidol + mefluidide severely injured centipedegrass, and seedhead suppression was poor regardless of date of treatment. Centipedegrass was severely injured when flurprimidol + mefluidide was applied at 1.68 + 0.28 kg·ha-1 in each of two applications, but seedheads were suppressed for 10 weeks. Imazethapyr applied at 0.30 and followed by 0.15 kg·ha-1 suppressed seedheads 10 weeks after treatment in 1987 and 6 weeks after treatment in 1988 without reducing turf density. When this PGR was applied as a single treatment at 0.30 kg·ha-1, seedhead suppression was generally greater for 8 weeks when applied mid- to late July than mid- to late June. Chemical names used: N-[2,4-dimethyl-5-[[(trifluoromethyl)sulfonyl]amino]phenyl]acetamide (mefluidide); α -(1-methylethyl)- α -[4-(trifluoromethoxy)phenyl]-5-pyrimidinemethanol (flurprimidol); and (±)-2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-5-ethyl-3-pyridinecarboxlic acid (imazethapyr).
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).
Daniel Hargey, Benjamin Wherley, Andrew Malis, James Thomas, and Ambika Chandra
species during the establishment period. PGRs are widely used in turf management for reducing shoot growth and frequency of mowing and/or seedhead suppression. TE is a commonly used PGR that reduces turfgrass shoot growth by inhibiting biologically active
Sonali R. Padhye and Judith K. Groninger
-ethyl for growth regulation of chrysanthemum ( Dendranthema × grandiflora ) HortScience 40 670 674 Fagerness, M.J. Penner, D. 1998 Evaluation of V-10029 and trinexapac-ethyl for annual bluegrass seedhead suppression and growth regulation of five cool
Paweł Petelewicz, Paweł M. Orliński, and James H. Baird
excellent growth suppression compared with PB or FP but do not result in effective annual bluegrass suppression. Nevertheless, TE can induce seedhead suppression; therefore, it is considered a positive addition to PGR mixes for annual bluegrass suppression
James T. Brosnan, Adam W. Thoms, Gregory K. Breeden, and John C. Sorochan
810 Kane, R. Miller, L. 2003 Field testing plant growth regulators and wetting agents for annual bluegrass seedhead suppression USGA Green Section Record. 41 21 26 Karcher, D. 2007 Digital
Xiuju Bian, Emily Merewitz, and Bingru Huang
absorbed quickly by foliage and slows cell elongation by inhibiting the conversion of one form of gibberellic acid (GA20) to another (GA1). TE has been used mainly for clipping reduction, seedhead suppression in annual bluegrass ( Poa annua L.), and
Yan Xu and Bingru Huang
), trinexapac-ethyl (TE; Syngenta Crop Protection, Greensboro, NC), has been widely used in turfgrass management for clipping reduction, seedhead suppression of annual bluegrass ( Poa annua L.), and improvement of overall turf quality in various turfgrass
Kevin Laskowski and Emily Merewitz
simulated winter conditions were used here, testing these treatments in the field may be important future research. Literature Cited Askew, S. 2017 Plant growth regulators applied in winter improve annual bluegrass ( Poa annua ) seedhead suppression on golf