Effect of Herbicides on the Production of Common Buffelgrass (Cenchrus ciliaris)

Abstract

Dicamba (3,6-dichloro-o-anisic acid), 2,4-D [(2,4-dichlorophenoxy)acetic acid], 2,4,5-T [(2,4,5-trichlorophenoxy)acetic acid], 3,6-dichloropicolinic acid, picloram (4-amino-3,5,6-trichloropicolinic acid), triclopyr {[(3,5,6-trichloro-2-pyridinyl)oxy] acetic acid}, tebuthiuron {N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea}, and hexazinone [3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4(1H,3H)-dione] were applied at rates of 0.3, 0.6, 1.1, and 2.2 kg/ha pre- and postemergence to greenhouse-grown common buffelgrass (Cenchrus ciliarisL. ♯3PESCI). Buffelgrass tolerated preemergence sprays of 3,6-dichloropicolinic acid up to and including 1.1 kg/ha. All other treatments except picloram and 2,4,5-T at 0.3 kg/ha were phytotoxic to emerging buffelgrass. Buffelgrass tolerated early postemergence applications of 2,4-D, picloram, and tebuthiuron at 0.3 kg/ha; dicamba and 2,4,5-T at 0.6 kg/ha; and 3,6-dichloropicolinic acid at 2.2 kg/ha based on oven-dry shoot production 1 month after treatment. Regrowth of buffelgrass from stubble 1 month after original harvest of the early postemergence treatment occurred only with all rates of 3,6-dichloropicolinic acid and 2,4,5-T at 0.3 kg/ha. When treated at 45 days after planting, buffelgrass tolerated dicamba, 2,4-D, 2,4,5-T, 3,6-dichloropicolinic acid, and picloram at 2.2 kg/ha, but top growth production was significantly reduced by most rates of hexazinone and tebuthiuron. Relative differences in regrowth of buffelgrass 1 month after the original harvest were similar to those of the original harvest. Mature buffelgrass (90 or 150 days old) responded similarly to herbicides as the 45-day-old buffelgrass.