Effect of nonylphenol ethoxylation on the biological activity of three herbicides with different water solubilities

Changing the number of ethylene oxide (EO) units on a nonylphenol surfactant changes its physicochemical and biological properties. Increasing the number of EO units makes the surfactant more hydrophilic and increases its hydrophilic-lipophilic balance (HLB). Surfactants with high HLB values, more than 16, were the most active with the hydrophilic herbicide glyphosate. More lipophilic surfactants with HLB values from 11 to 13 were more active with the lipophilic herbicide, the ethyl ester of quizalofop-P. Surfactants with intermediate HLB values were the most active with the herbicide that had intermediate water solubility, nicosulfuron. Matching the physicochemical properties of the herbicide and surfactant improved biological efficacy on giant foxtail.