Response of perennial ryegrass, prairie grass, and browntop to the growth retardant, mefluidide

Abstract The efficacy of the synthetic growth retardant mefluidide in reducing grass sward yield is affected by the interactions of plant species, chemical, and environmental factors. This field study examines the effect of mefluidide on the growth and development of 3 grass species; perennial ryegrass ( Lolium perenne L.), prairie grass ( Bromus catharticus Varth.), and browntop ( Agrostis tenuis Sibth.). All 3 species were significantly retarded for up to 8 weeks by a single application of mefluidide at 0.5 kg/ha or higher. Both vegetative and reproductive development were suppressed by mefluidide. Some mefluidide‐induced phytotoxicity was observed, particularly in the finer‐leaved browntop species. In a second field experiment, the timing of mefluidide application was noted to have a significant effect on efficacy. Early spring applications during September were the most effective, although significant retardation of grass growth was also observed following later applications in October.