Varying the type of nonionic surfactant greatly changed the biological activity of the ethyl ester of quizalofop-P on giant foxtail, barnyardgrass, and corn. These studies statistically evaluated 22 surfactants with widely different chemical, physical, and surface properties. Of the 14 surfactant properties analyzed, dynamic surface tension was the most important to enhance quizalofop-P activity. Alcohol ethoxylate surfactants like Genapol® 24-L-92 and Tergitol® 15-S-7 were among the most effective adjuvants. These surfactants performed significantly better than the commercial nonionic surfactant, Induce®, and equal to a high-quality petroleum crop oil concentrate, Agri-dex®. These surfactants offer a lower dose option to crop oil concentrates and a more effective surfactant alternative for mixtures that prohibit crop oil concentrates.