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Published online by Cambridge University Press: 12 June 2017
Several herbicides were evaluated for the control of velvet lupine (Lupinus leucophyllus Dougl. #3 LUPLE), a plant poisonous to sheep on western mountain ranges, and a secondary target species, mountain big sagebrush [Artemisia tridentata Nutt. # ARTTR]. Change in foliar cover of the two target species and associated vegetation was used to evaluate efficacy of the herbicides. Velvet lupine cover was reduced by greater than 50% in the 1983 trial by the butyl ester of 2,4-D [(2,4-dichlorophenoxy)acetic acid] at 2.2 and 4.5 kg ae/ha, the butoxyethanol ester of 2,4,5-T [(2,4,5-trichlorophenoxy)acetic acid] at 1.1 and 2.2 kg ae/ha, the dimethylamine salt of dicamba (3,6-dichloro-2-methoxybenzoic acid) at 2.2 kg ae/ha, and 2,4-D plus dicamba at 1.1 plus 0.6 kg/ha. Cover of velvet lupine and other forbs was reduced by drought in the spring of 1985 and obscured the comparison among herbicides in the 1984 trial. Cover of mountain big sagebrush was consistently reduced (>88%) by 2,4-D at 4.5 kg/ha in both trials, and by three rates of the butoxyethyl ester of triclopyr {[(3,5,6-trichloro-2-pyridinyl)oxy] acetic acid} (>67%) in the 1984 trial. Grass cover increased in plots where herbicides effectively reduced velvet lupine, forbs, and mountain big sagebrush.