Weed populations in the main cultures of Luxembourg: control options and monitoring in a complex environmental and political framework

Abstract

Due to ecotoxicological and environmental reasons, chemical treatments for weed control are under discussion. To help farmers in coping with challenges imposed by restricted herbicide availability, projects on using modified crop rotations for reducing weed pressure, digital approaches for better decision support, and a better integration of non-chemical weeding were initiated. First monitoring programs in winter oilseed rape in Luxembourg offered a preliminary overview about mainly widespread weed species like Stellaria media, Viola arvensis, Polygonum aviculare as well as Poa annua, Elymus repens and Apera spica-venti. Chenopodium album was found in moderate and high numbers in maize, as well as the spring-germinating Polygonum species. Polygonum convolvulus escaped from or re-emerged after the chemical control at location Kuborn, while C. album was poorly controlled by the mechanical treatments. Alopecurus myosuroides plants with mature seeds were almost exclusively found in the South of Luxembourg. All 35 A. myosuroides seedling samples tested so far were resistant towards Stomp® Aqua (containing the microtubule assembly inhibitor pendimethalin). In case of Sigma® Maxx (containing the ALS inhibitors iodosulfuron+mesosulfuron), 2 out of 35 samples were sensitive and moderately resistant, respectively. 31 samples were resistant to Sigma® Maxx. 17 out of 35 samples were sensitive to Axial® (containing the ACC-ase inhibitor pinoxaden), while 18 samples were resistant to Axial®.