Evolution of a herbicide-resistant population of Alopecurus myosuroides Huds. in a long-term cropping system experiment

Due to heavy reliance oil herbicides and a lack Of Cultural Control measures, herbicide-resistant populations of Alopecurus myosuroides Huds. (blackgrass) appeared in the early 1990s in winter cereal rotations in France and in Europe. The aim of the present study was to analyse the effects of different cropping systems oil an aryloxy-phenoxypropionate herbicide-resistant population in a field trial. Two crop rotations, one consisting exclusively of winter crops and another including spring crops, were assessed over a six-year period. The rotations were combined with different cuitural practices including mouldboard Ploughing, delayed sowing, and efficient herbicides for controlling resistant plants. A. myosuroides densities decreased in all the cropping systems, but the weed management was most effective when herbicides were combined with non-chemical practices. Rotation with an alternation of spring and winter crops was the most efficient solution against A. myosuroides. Moreover. during the six years, the percentage of resistant plants in different crop rotations was estimated independently of the cropping systems. This proportion did not vary during the six years of the experiment, suggesting that the resistance gene persisted, despite the removal of selection pressure by the aryloxy-phenoxypropionate herbicides. (C) 2008 Elsevier Ltd. All rights reserved.