Precision agriculture has emerged as a revolutionary technology in helping make farm decisions. It transforms farm related data into information, and then coverts information into useful knowledge for decision-making. This study evaluates economic thresholds for a new web-based decision support system developed for precision fungicide management for potato production. Using 10 years of computer simulation experiments from 152 locations in the United States, we compared different thresholds in terms of disease severity, fungicide usage efficiency, and net income over fungicide cost to manage potato late blight disease. The empirical results show that the economic thresholds improved disease suppression and farming profit relative to the previous critical thresholds while maintaining fungicide use efficiency.