Broadleaf herbicide effects on tall fescue (Festuca arundinacea) seedhead density, forage yield, and quality

Four broadleaf herbicides and combinations were compared for two years with mefluidide, a growth regulator, for effects on 'Ky 31' and 'Fawn' tall fescue. Seedhead densities averaged 33% of the check with 8.4 g ai/ha of metsulfuron, 17% with 70 g ai/ha of imazethapyr, and 9% with 280 g ai/ha of mefluidide, while forage yields were reduced to about 40% of the check. Forage crude protein (CP) concentrations were increased by mefluidide, imazethapyr, and 8.4 g/ha of metsulfuron. Neutral-detergent fiber (NDF) of Ky 31 but not Fawn forage was reduced by mefluidide, imazethapyr, and metsulfuron at 6.3 and 8.4 g/ha, but Fawn NDF was increased by dicamba plus 2,4-D. In vitro dry matter digestibility was increased by metsulfuron at 6.3 and 8.4 g/ha, mefluidide, and imazethapyr in one of two years. Adding 2,4-D to metsulfuron reduced some effects of metsulfuron. Total CP/ha was no more adversely affected by imazethapyr and metsulfuron than mefluidide. Imazethapyr and metsulfuron can thus be used to control weeds without reducing fescue forage value. Nomenclature: Dicamba, 3,6-dichloro-2-methoxybenzoic acid; imazethapyr, 2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-5-ethyl-3-pyridinecarboxylic acid; mefluidide, N-[2,4-dimethyl-5-[[(trifluoromethyl)sulfonyl]-amino]phenyl]acetamide; metsulfuron, 2-[[[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino]carbonyl]amino]sulfonyl]benzoic acid; 2,4-D, (2,4-dichlorophenoxy)acetic acid; tall fescue, Festuca arundinacea Schreb.