Chlorotoluron -: re-introduction of a compound with great importance to manage herbicide resistance in blackgrass (Alopecurus myosuroides Huds.)

Black grass is a hard-to-control grass, especially in areas with crop rotation of cereals and oilseed rape. Besides cultivation practice, alternating use of herbicides with different modes of action in tank mix or spraying course is the most important measure for achieving a sustainable control and prevention of resistance development. The urea derivatives Isoproturon (IPU) and Chlorotoluron (CTU) are belonging to the herbicides most frequently used in Europe against the grass. While IPU has been used in Germany since more than 40 years without interruption, registration of CTU-containing formulations has expired in 1998. For Lentipur CL 700, a 700 g/l Chlorotoluron SC formulation, the registration in Germany is expected for June 2006. In trials conducted in parallel to the registration process, the efficacy of the formulation alone and in tank mixture with Ralon Super was tested at post emergence timing in autumn. The trials showed, that the combination of 2,0 l/ha Lentipur CL 700 with 1,0 l/ha Ralon Super is providing a high level of safety for black grass control also under difficult conditions. Investigations on sensitivity of black grass samples against CTU in the greenhouse revealed results correlating to that on field efficacy of Lentipur CL 700.