Biodiversity-based options for arable weed management. A review

In the context of a shift towards pesticide reduction in arable farming, weed management remains a challenging issue. Integrated Weed Management currently recommends agronomic practices for weed control, but it does not integrate the use of biodiversity-based options, enhancing the biological regulation of weeds. Here, wereview existing knowledge related to three potentially beneficial interactions, of crop-weed competition, weed seed granivory, and weed interactions with pathogenic fungi. Our main finding are the following : (1) promoting cropped plant-weed competition by manipulating cropped cover could greatly contribute to weed reduction; (2) weed seed granivory by invertebrates can significantly lower weed emergence, although this effect can be highly variable because seed predation is embedded within complex multitrophic interactions that are to date not fully understood; (3) a wide range of fungi are pathogenic to various stages of weed development, but strain efficacy in field trials does not often match that in controlled conditions. We present a framework that superimposes biodiversity-based options for weed biocontrol on a classical Integrated Weed Management system. We then describe the current state of knowledge on interactions between agronomic practices and the organisms at play and between the different biological components of the system. We argue that further advances in our understanding of biodiversity-based options and their performance for weed biocontrol will require farm-scale experimental trials.