Optimizing Sulfosulfuron and Sulfosulfuron Plus Met sulfuron- methyl Activity when Tank-Mixed with Vegetable Oil to Control Wild Barley ( Hordeum spontaneum Koch.)

Abstract

Wild barley has invaded wheat fields ever since fla mprop-isopropyl was outdated in Iran. Newly developed herbicides such as sulfosulfu ron or sulfosulfuron plus metsulfuron- methyl can control it at higher than recommended do sages, but causing significant wheat injury. Hence, two dose-response experiments were c onducted to evaluate their efficacy when tank-mixed with thirteen different vegetable o ils, at the Ferdowsi University of Mashhad, Iran, during 2013. Moreover, a wheat culti var (Gaskogen) was also treated with effective dose of 90% (ED 90 ) of both herbicides (21.44 grams active ingredient (g ai) of sulfosulfuron ha -1 and 41.95 g ai of sulfosulfuron plus metsulfuron-m ethyl ha -1 ) with and without each vegetable oil to check selectivity . Averaged over vegetable oils, the effective dose of 50% (ED 50 ) was decreased 2.6- and 3.0-fold with sulfosulfuro n and sulfosulfuron plus metsulfuron-methyl, respectively . Among the evaluated vegetable oils, cottonseed and coconut oil were the best ones to en hance the efficacy of both herbicides. The castor oil had the least effect. A negative cor relation was observed between the efficiency of vegetable oils and its unsaturated/sa turated fatty acids ratio. No phytotoxic effect on wheat was observed when these herbicides were applied with or without the vegetable oils. Keywords : Crop selectivity, Herbicide efficacy, Penetrant a gent, Vegetable oils, Wild barley.