Ryegrass (Lolium rigidum Gaud.) developed resistance to Acetolactate Synthase (ALS) and Acetyl-CoA Carboxylase (ACCase) inhibiting herbicides. The objective is to evaluate the effect of the active substance 'Prosulfocarb', sprayed, in post-sowing preemergence, at different doses and associated with S-metolachlor. Therefore, to evaluate its effect on ryegrass resistant to the registered rate (3200 g ha-1) and according to the stages of application (SAP1: 1 day after sowing of wheat, SAP2: 7 days after sowing and SAP3: 2 to 3 leaves after emergence). To study the effect of Prosulfocarb and post-emergence herbicides on the yield of durum wheat and its components. To meet these objectives, field trials were installed in northern Tunisia (Mateur/Bizerte), with a Randomized Complete Bloc Design (RCBD). The evaluation was carried out over 3 successive seasons (2012/13 to 2014/15).  The data collected are the subject of the analysis of variance (ANOVA). The results revealed that the efficacy of prosulfocarb changes with increasing application rates. The S-metolachlor favored the improvement of prosulfocarb efficacy by 6 to 15%. The results also showed that the efficacy of prosulfocarb was better in the first two stages of the application (SAP1 and SAP2) and low in application after emergence (SAP3). Prosulfocarb allowed a gain of 7.3% in the yield of durum wheat. The ryegrass infestation (92.5 plants / m²) affected the number of grains per spike and slightly affected the PMG of durum wheat and caused yield losses that can reach 39%.

Key words: Herbicide, Loss, Prosulfocarb, Ryegrass, Yield, Resistance, Tunisia.