Regrowth phenomenon of wild oat after application herbicide in two populations Fars and Kurdistan

To evaluate the different doses of mesosulfuron + iodosulfuron (Atlantis) and application time on two Kurdistan and Fars populations in crop year 2013-2014, a split spilt plot experiment was carried out in the field in Fars province. The different doses of herbicide (0, 6, 12, 18, 24 g ai/ha) as the main plot, two populations of wild oat (Kurdistan and Fars respectively) as sub-plot and application time at stages of 18 (8 leaves) and 23 zadoks (tillering) as sub-sub plot were considered. The regrowth percentage of wild oat Fars and Kurdistan populations in highest dose (24 g ai/ha) at two herbicide application times in 8 leaves (16.16 and 4.5%) and tillernig (23 and 6%) were obtained respectively. It is remarkable that the regrowth percentage of wild oat at reduced dosage (12 g ai/ha) at tillernig time was more than 8 leaves in two Kurdistan and Fars populations. Dose-response equations for dry weight of wild oat showed that the required level of dose for reaching a 50% decrease in two populations of wild oat and application times was different. Doses of 7.93 and 8.38 g ai/ha in order to achieve a 50% decrease in the dry weight of Kurdistan population in two application times of 8 leaves and tillering was required. These amounts for a 50% reduction in dry weight of Fars were 9.89 and 9.66 g ai/ha, respectively. In reduced doses of herbicide with delayed application time, regrowth and dry weight of wild oat increase and effect on grain yield and number of spike in wheat. The application of reduced doses (12 g ai/ha) is recommended at stages of 18 zadoks (8 leaves).