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Huisache (Acacia farnesiana) is a small tree that has become a pest on many rangelands throughout the southern third of Texas.  Huisache is expanding in density and range and is difficult to control via herbicide or mechanical methods due to vigorous resprouting. The objective of this research was to characterize the optimal timing for control of huisache by discerning seasonal changes in root nonstructural carbohydrate concentration. Four study sites were selected in the Coastal Bend Area of Texas, based on differences in soil type.  Phenological stage was determined by examining 20 shrubs (> 2 m height) per site and all shrubs used for this study were in the same phonological stage on the date of measurement. Five shrub root samples were taken from each site every month for drying and grinding for laboratory analysis. Laboratory procedures consisted of total nonstructural carbohydrate (TNC) analysis using anthrone reagent and spectrophotometry. Five to ten shrubs per site per month were sprayed with two different herbicide formulations. Root total nonstructural carbohydrate concentration, weather station data (precipitation, soil moisture, soil temperature, and air temperature), shrub mortality two growing seasons following herbicide application, and phenological stage were subjected to analysis of variance. Duncan's multiple range test was used to separate mean differences when significant F-values were found. We correlated shrub mortality with root TNC content and found mortality was greatest when root TNC was increasing. Understanding the timing of root carbohydrate translocation will allow better chemical control of this rangeland pest.