It is possible to increase the efficacy of herbicides by adding vegetable oils to the spray tank. In order to evaluate and study this fact a greenhouse study was conducted. Three vegetable oils: coconut, sesame and almond oils at 0.3% (v/v) were applied to compare their influence on enhancing the efficacy of pinoxaden and haloxyfop-R-methyl on littleseed canarygrass Phalaris minor Retz. (Poaceae) control, in 2012. The experimental design was completely randomized design with six replications in a factorial arrangement for each herbicide. The factors for each herbicide included vegetable oils in three levels and herbicide dose at six levels (0, 6, 12.5, 25, 50 and 100 percent of recommended doses). The results of experiment revealed that by adding each vegetable oils haloxyfop-R-methyl ester weed suppressing influence was further increased compared to pinoxaden which was attributed to a positive relationship between oil receptivity and the high octanol–water partition coefficient of haloxyfop-R-methyl ester herbicide. Among the evaluated vegetable oils, coconut oil had the highest ability to enhance the efficacy of the two herbicides.

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