Evaluation of cropping systems for management of herbicide-resistant populations of blackgrass ( Alopecurus myosuroides Huds.)

Abstract

Simplification of cropping systems often leads to an increase in weed populations which require an intensive use of herbicides to maintain populations at an acceptable level. Due to a heavy reliance on herbicides and a lack of cultural control measures, herbicide-resistant blackgrass ( Alopecurus myosuroides Huds.) biotypes appeared recently in France. An experiment was conducted to evaluate the effects of different cropping systems on a population of herbicide-resistant blackgrass. Two crop rotations, one consisting exclusively of winter crops and another including spring crops, were assessed over a three-year period. Crop rotation was combined with different cultural practices (mouldboard plough, delayed sowing dates, reduced nitrogen fertiliser applications and effective herbicides on resistant blackgrass). Blackgrass densities decreased in all the cropping systems, but blackgrass control by herbicides was most effective when combined with non-chemical practices. The benefits of the different weed management systems are discussed in relation to their effect on blackgrass density and their cost to the farmer. In our conditions, the introduction of spring crops into the rotation gave the best results, both from an economical and weed management point of view.