The effect of herbicides on the concentration of miserotoxin, the toxic compound in Wasatch milkvetch [Astragalus miser var. oblongifolius (Rydb.) Cronq. # ASAMO], was investigated. Eight herbicides or herbicide combinations were applied to Wasatch milkvetch in June 1985 and 1986. The concentration of miserotoxin was determined weekly for 4 weeks after treatments. All treatments in both years significantly reduced the miserotoxin concentration when compared to the controls, except for the 0.6 kg ae/ha rate of clopyralid (3,6-dichloro-2-pyridinecarboxylic acid) in 1986. Wasatch milkvetch treated with triclopyr {[(3,5,6-trichloro-2-pyridinyl)oxy] acetic acid} at 1.7 and 2.2 kg ae/ha desiccated rapidly and had consistently low concentrations of miserotoxin 4 weeks after treatment.

Eight herbicides or herbicide combinations were evaluated for control of Wasatch milkvetch and other broadleaf plants. Triclopyr at 2.2 kg ae/ha controlled Wasatch milkvetch and associated mountain big sagebrush and mulesears 100%. A combination of triclopyr plus dicamba at 1.1 plus 1.1 kg ae/ha also controlled these species. When compared to untreated plots, grass production increased over 400% on plots treated with triclopyr at 1.7 and 2.2 kg/ha and more than 300% on plots treated with triclopyr plus dicamba at 1.1 plus 1.1 kg/ha.