Alopecurus myosuroides dynamics simulated with ALOMYSYS for the reference cropping system (see table 2 for details) as a function of herbicide treatment conditions. Rotation is winter oilseed rape / winter wheat/winter barley with a mouldboard ploughing every 6 years before oilseed rape (triangles). Means and standard-errors from ten repetitions with randomly chosen weather series from Dijon, Burgundy (5°2’E, 47°20’N). The rectangle indicates the years over which is calculated the medium-term infestation.