| Current use patterns for synthetic plant growth regulators (PGRs) in bermudagrass (Cynodon sp.) have illustrated these compounds may have diverse functions in turfgrass beyond the scope of what is recommended. Studies were conducted in bermudagrass to investigate the effect of PGRs on the following: (1) transition into fall dormancy and interactions with variable growth temperatures, (2) nitrogen and water use efficiency, (3) lateral development and vegetative establishment, and (4) thatch accumulation. All studies featured trinexapac-ethyl, a gibberellic acid biosynthesis inhibitor while some studies also featured similar compounds such as ethephon or paclobutrazol. Results suggested the following for each study: (1) bermudagrass responses to trinexapac-ethyl at suboptimum temperatures help explain fall field observations through indications of enhanced ecological fitness, (2) trinexapac-ethyl reduces clipping nitrogen but does not promote reduced water use or increased nitrate loss, (3) PGRs stimulate lateral development through alteration of canopy architecture or stolon growth and may thereby assist bermudagrass sprig establishment, particularly at locations with limited irrigation, and (4) trinexapac-ethyl changes canopy architecture, not thatch, to improve mowing quality. While some new prospective field benefits for PGRs were suggested, the scope of this research principally indicated that normal use patterns of trinexapac-ethyl are devoid of unwanted side effects, either directly or indirectly through manipulation of bermudagrass ecology. |
