Does increase of wild oat density change time of application of wheat selective herbicide?

To investigate the effrct of various densities of wild oat, application time and type of herbicide on wild oat control and yield and yield components of wheat, a split spilt plot experiment was carried out base on randomized complete block design (RCBD) with 3 replications in a field in Fars Province )Marvdasht city) in the cropping year of 2014-2015. The different densities of wild oat (0, 20, 40, 80, 160 and 320 plants m2) as the main plot, two herbicides including mesosulfuron + iodosulfuron + mefenpyr-diethyl (Atlantis18 g a.i. /ha) and clodinafop-propargyl (Topik, 64 g a.i. /ha) as sub-plot and application time (18 (8 leaves) and 23 Zadoks (tillering) stages) as sub-sub plot were considered. According to logistic model (parameter Den50), 127 and 95 wild oats per m2 was required to reach a 50% reduction in dry weight of wild oat in clodinafop-propargyl herbicide treatment at 8 and 23 Zadoks stages, respectively, whereas, for 50% reduction in dry weight of wild oat in mesosulfuron + iodosulfuron herbicide treatment were 141 and 149 wild oats/m2, respectively. The regrowth of wild oat in clodinafop-propargyl compared to mesosulfuron + iodosulfuron herbicides was higher in tillering compared to 8 leaves in all densities. Hyperbolic model for grain yield showed that in Topik herbicide treatment at both application times, 50% reduction in the yield was observed in 118 and 83 wild oats/m2 and in mesosulfuron + iodosulfuron herbicide treatment at both application times, 50% reduction in the yield was observed in 423 and 221 wild oats/m2.At higher wild oat densities, of mesosulfuron + iodosulfuron application is recommended at 18 Zadoks stage.