Low Effectiveness of Prosulfocarb and Mesosulfuron-Methyl + Iodosulfuron-Methyl against .

Due to natural tolerance to most widely used herbicides for grass weed control, prosulfocarb as pre-emergence or early post-emergence herbicide and mesosulfuron + iodosulfuron as post-emergence herbicide are the mainstays of any chemical control program for in Denmark. However, farmers often report variable efficacy of these herbicides on compared to other grass weeds. Dose-response experiments were conducted to evaluate the performance of prosulfocarb and mesosulfuron + iodosulfuron on Prosulfocarb was sprayed at different plant growth stages to study the influence of plant growth stage on the performance of prosulfocarb on in comparison with the more susceptible grass weed species . Doses causing 50% reduction in response variable (ED) were estimated from the dose-response analysis. The ED values revealed a higher tolerance of to prosulfocarb and mesosulfuron + iodosulfuron than The relative difference in the effectiveness of prosulfocarb between and was constant among plant growth stages studied. The highest levels of control were achieved when prosulfocarb was sprayed pre-emergence (BBCH 00), while the control substantially declined at later growth stages. The results from the current study document the tolerance of to prosulfocarb and mesosulfuron + iodosulfuron and highlight the importance of optimization of prosulfocarb spray timing for achieving maximum control of .