Adapting cropping system to delay herbicide resistance. A simulation study

EA SPE EcolDur GEAPSI CT1 (SPE)International audienceWeeds have evolved resistance to numerous herbicides, and their management becomes increasingly expensive and difficult. Here we (1) adapted the existing weed dynamics simulation model AlomSys to account for target-site resistance to acetyl-coenzyme A carboxylase (ACCase)-inhibiting herbicides in Alopecurus myosuroides by integrating wild and mutant target-site resistant (TSR) genotypes, mutations, fitness costs and seed immigration, and (2) ran simulations testing different crop management practices for their ability to delay resistance evolution and/or control of TSR plants. Simulations of an oilseed rape/winter wheat/winter barley rotation showed that TSR plants exceeded 1 plant/m² approximately 22, 7 and 7 years after introducing one, several or many selective herbicides, respectively. Reduced herbicide rates or spraying conditions had no effect on the selection of TSR plants; adding spring pea to the rotation, yearly mouldboard ploughing, occasional ploughing before wheat or rapeseed delayed resistance by 14, 12, 7 and 3 years, respectively. Allele proportions also changed, e.g. ploughing selected a hitherto rare TSR allele presenting improved pre-emergent growth