Prohexadione Ca (calcium salt of 3,5-dioxo-4 propionylcyclohexane-carboxylic acid) inhibits the same enzyme as trinexapac-ethyl and is currently marketed in agricultural crops such as peanut and apples.  This growth regulator has not been previously evaluated in turfgrass.  Following several greenhouse studies, separate field trials were repeated three times to evaluate effects of prohexadione Ca rate on percent clipping biomass reduction of bermudagrass [Cynodon dactylon (L.) Pers. cv. Vamont], Kentucky bluegrass (Poa pratensis L. cv. Kelly), perennial ryegrass (Lolium perenne L. cv. Prosport), and zoysiagrass (Zoysia japonica Steud. cvs. Korean Common and Meyer).  The manufacturer’s recommended trinexapac-ethyl rate and sequential treatment timing for each turfgrass species was included as a comparison.  Percent clipping biomass reduction increased in all species with increasing prohexadione Ca rates between 0.14 and 0.67 kg ai/ha-1 when two treatments were applied at a 3 week interval.  When averaged over prohexadione Ca rate, percent clipping biomass reduction peaked at two and five WAIT for perennial ryegrass and zoysiagrass, five WAIT for Kentucky bluegrass, and at one WAIT for bermudagrass.  When compared to the recommended rates of trinexapac ethyl applied twice at a 4 week interval, prohexadione Ca reduced clipping biomass of bermudagrass, Kentucky bluegrass, perennial ryegrass, and zoysiagrass equivalently when applied at 0.70, 0.22, 0.60, and 0.27 kg a.i. ha-1, respectively.  These data suggest prohexadione Ca effectively suppresses turfgrass clipping biomass comparable to trinexapac-ethyl and could be a viable plant growth regulator for the turfgrass industry.

Abbreviations.  PGR, plant growth regulator; WAIT, weeks after initial treatment.

Citation:  Beam, J. B. and S. D. Askew.  2005.  Prohexadione calcium effects on bermudagrass, Kentucky bluegrass, perennial ryegrass, and zoysiagrass.  Int. Turf. Soc. Res. J. 10:286-295.