The Impact of Ryegrass Density and Different Herbicides on Wheat Yield and Efficacy of Various Herbicides against Ryegrass

Herbicides are used to control ryegrass (Lolium rigidum Gaud.) in cereals. In 2011/12, an experiment was conducted in Mateur, to evaluate the effect of herbicide treatments on ryegrass biomass and wheat (Triticum durum Desf.) yield. Similarly, a second experiment was conducted in five locations (Mateur, Fritissa, Metline, Tinja and Menzel Bourguiba) to quantify the losses caused by ryegrass to wheat yield. The results of the first experiment showed that Tolurex proved the most effective in reducing ryegrass biomass by 96.4%. The analysis of variance showed significant effect of herbicide treatments on wheat yield. The highest wheat yield was recorded with Tolurex (6.15 t ha-1 ), which improved the yield by 59%. The results of the second experiment indicated that the highest losses in ryegrass biomass were recorded with Menzel Bourguiba (1.5 t ha-1 ) with average density of ryegrass (393 plants m-2 ). The lowest losses (0.38 t ha-1 ) in ryegrass biomass were recorded with Metline, heavily infested with ryegrass (450 plants m-2 ). Yield of wheat was not correlated (r = 0.18 and p = 0.77) with ryegrass density. The average loss in yield was 0.9 t ha-1 (±0.4) with an average density of more than 390 plants m- 2. Tolurex, inhibitor of photosystem II (PSII), reduced ryegrass biomass, while improved wheat yield. It is recommended to use Tolurex for the control of ryegrass in the north of Tunisia. Moreover it is suspected that ryegrass has evolved resistance against commonly used acetyl Coenzyme A carboxylase (ACCase) and acetolactate synthase (ALS) inhibitor hericides