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Huisache (Acacia farnesiana�[L.] Willd.), a pest tree species on rangelands throughout the southern third of Texas, is expanding in range and density, displacing forage grasses and forbs, and resisting control via herbicide, fire, or mechanical methods through vigorous resprouting and prolific seed production. The objectives of this research were to characterize the optimal timing and environmental conditions for effective herbicide control. Four huisache-invaded pastures with different soil textures from four counties along the Texas Coastal Bend region were used in this study. On-site weather station data was gathered, and average phenological stage of huisache was determined each month for each pasture; shrubs from the average phenological stage were used for TNC (total nonstructural carbohydrate) analysis and herbicide treatment. Each month between April 2012 and November 2014, five shrubs per site were excavated and the root crowns were collected, frozen, dried, ground, and analyzed for TNC. In addition, two herbicide formulations were foliar-applied to five to ten shrubs every month at the four sites, and mortality was evaluated following two growing seasons. Data were analyzed using a randomized complete block design ANOVA (using study site as a blocking factor), with appropriate post hoc tests used to separate means. Root crown TNC results reveal significant increases (compared to the prior month) during May, August, and December. Increases in TNC from one month to the next result from translocation of TNC from aerial portions of the plant into the root crown; in other weedy species foliar application during downward translocation of TNC has increased mortality of treated plants. Herbicide-induced mortality was greatest during the months of October, May, November, and September.