optimizing sulfosulfuron and sulfosulfuron plus metsulfuron-methyl activity when tank-mixed with vegetable oil to control wild barley (hordeum spontaneum koch.)

Wild barley has invaded wheat fields ever since flamprop-isopropyl was outdated in iran. newly developed herbicides such as sulfosulfuron or sulfosulfuron plus metsulfuron-methyl can control it at higher than recommended dosages, but causing significant wheat injury. hence, two dose-response experiments were conducted to evaluate their efficacy when tank-mixed with thirteen different vegetable oils, at the ferdowsi university of mashhad, iran, during 2013. moreover, a wheat cultivar (gaskogen) was also treated with effective dose of 90% (ed90) of both herbicides (21.44 grams active ingredient (g ai) of sulfosulfuron ha-1 and 41.95 g ai of sulfosulfuron plus metsulfuron-methyl ha-1) with and without each vegetable oil to check selectivity. averaged over vegetable oils, the effective dose of 50% (ed50) was decreased 2.6- and 3.0-fold with sulfosulfuron and sulfosulfuron plus metsulfuron-methyl, respectively. among the evaluated vegetable oils, cottonseed and coconut oil were the best ones to enhance the efficacy of both herbicides. the castor oil had the least effect. a negative correlation was observed between the efficiency of vegetable oils and its unsaturated/saturated fatty acids ratio. no phytotoxic effect on wheat was observed when these herbicides were applied with or without the vegetable oils.