Is the regrowth of Avena spp. after herbicide application affected by the application time?

A factorial experiment based on randomized complete block design (RCBD) with three replications in two fields in Marvdasht city (Fars province, Iran) was conducted to evaluate the effect of different herbicides at different times based on growing degree day (GDD) Avena spp. controlling. The first factor was five selective wheat herbicides including clodinafop-propargyl (Topik 64 g a.i./ha), fenoxaprop-p-ethyl (Pumasuper, 75 g a.i./ha), mesosulfuron + iodosulfuron + safener mefenpyr-diethyl (Atlantis, 18 g a.i./ha), sulfosulfuron (Apirus, 20 g a.i./ha), and metsulfuron methyl + sulfosulfuron (Total, 30 g a.i./ha). The second factor was application time of herbicide at 19 (398 GDD), 23 (435 GDD), 29 (502 GDD) and 31 (618 GDD) zadoks stages. Increasing GDD (from 398 to 618 GDD) increased regrowth percentage and dry weight of Avena spp. The maximum   regrowth percentage and dry weight of Avena spp were observed in clodinafop-propargyl, fenoxaprop-p-ethyl and sulfosulfuron herbicides treatments while they were applied at the 618 GDD (Zadoks 31). The minimum regrowth percentage (26%) was obtained in mesosulfuron + iodosulfuron herbicide treatment at the 398 GDD (Zadoks 19). The highest grain yield (>5664 Kg/ha) was obtained using metsulfuron methyl + sulfosulfuron and mesosulfuron + iodosulfuron at the 435 GDD. The mesosulfuron + iodosulfuron (Atlantis) herbicides treatment controlled Avena spp appropriately at the 398 GDD, however it led to wheat leaf burning due to the dry conditions, so that a 50%  yield reduction (2679 Kg/ha) occurred in comparison to the 435 GDD. It is recommended that the early application of metsulfuron methyl + sulfosulfuron and mesosulfuron + iodosulfuron (435 GDD) with regard to weather conditions may reduce the wheat grain yield loss and Avena spp regrowth.