optimizing the efficacy of sulfosulfuron and sulfosulfuron + mesosulfuron-methyl herbicides to control wild barley (hordeum spontaneum koch.) in wheat with adjuvants

wild barley (hordeum spontaneum) has invaded to wheat and barley fields since flamprop-isopropyl was obsolesced in iran. the herbicides of sulfosulfuron and sulfosulfuron + metsulfuron-methyl are able to control it at higher-than-recommended dosages, causing a crop injury. hence, two dose-response experiments in factorial experiment with a completely randomized design with four replications were conducted to enhance the efficacy of them by adding 9 adjuvants in faculty of agriculture, ferdowsi university of mashhad, iran in 2013. the treatments included six doses of each herbicide with and without each adjuvant. moreover, a cultivar of wheat (gaskogen) was treated by the doses of both herbicides with and without each vegetable oil, the ed90s, to check selectivity. according to relative potency values, adigor and propel were the most effective adjuvant to enhance the efficacy of sulfosulfuron and sulfosulfuron + metsulfuron-methyl, respectively. in contrast, ammonium nitrate and d-octil were the least effective adjuvant to enhance the efficacy of sulfosulfuron and sulfosulfuron + metsulfuron-methyl, respectively. selectivity of both herbicides was not changed by applying adjuvants. whereas penetrate agents had the greatest efficiency among the adjuvants can be stated that probably relative tolerance of wild barley, in addition to herbicide degradation, is due to physicochemical properties of the leaf cuticle.