A nonionic (Citogate) and cationic (Frigate) surfactant were evaluated for their efficacy to enhance clodinafop-propargyl performance and minimize rainfall effect in controlling wild oat (Avena ludoviciana Durieu.). Moreover, by using the capillary rise technique the surface tension of these surfactants or surfactants plus clodinafop-propargyl aqueous solution was determined. Lower and higher surface tension values were recorded with aqueous solution of Citogate and Frigate alone and along with clodinafoppropargyl, respectively. The critical micelle concentration of Citogate (0.15% v/v) was higher than of Frigate (0.1% v/v). Both the tested surfactants minimized the rainfall effect and improved the performance of clodinafop-propargyl on wild oat. When Citogate was added to clodinafop-propargyl, herbicidal activity was higher than when Frigate was added, indicating that the surfactants potency to reduce surface tension of spray solution is a momentous factor in order to enhance clodinafop-propargyl performance. The data from rainfall treatment have confirmed this hypothesis, as it seems when Citogate was added to clodinafop-propargyl; rainfall adverse effect was lower which is presumably due to quick absorption of clodinafop-propargyl by wild oat leaves. In other words, clodinafop-propargyl infiltrated in short-term before it was washed off the wild oat leaf surface as a hypothesis.

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