Increased efficacy of clodinafop-propargyl by terpineols and synergistic action with esterified fatty acids

Abstract

A novel chemistry, namely terpene alcohols from pine tree (Pinus pinaster Ait.) was assessed as adjuvants for herbicides. The compared adjuvants included butylated fatty acids from tall oil, a blend of terpene alcohols, mainly isomers of terpineols, from pine oil and three mixtures containing butylated fatty acids and terpineols. All were emulsified with the same non-ionic vegetable surfactant present at 25% (wt/wt). Whole-plant bioassays were performed in the greenhouse with Alopecurus myosuroides Huds. and oats to compare the effects of these vegetable-based adjuvants on the efficacy of clodinafop-propargyl. Formulated clodinafop-propargyl, with its safener and adjuvants added in tank-mixture, was applied at the 2-leaf stage of the plants. The effects of adjuvants were compared on the basis of doses of herbicide producing the same effect. Herbicide efficacy was increased less than twofold by the emulsifier, 2--3-fold by butylated seed oil and 5-6-fold by terpineols. The optimum effect of terpineols was observed at 0.5% (V/ V). The addition of terpineols to butylated fatty acids (mixture ratio 0.5:0.5; wt/wt) increased the effect of esterified fatty acids up to the level of terpineols. A synergistic joint action was demonstrated when analysed with the Additive Dose Model. The interest of terpineols as adjuvants of herbicides is discussed.