Toward a better prediction of in-field weed regulation by carabid beetles in European arable landscapes

Prod 2019-70d SPE GESTAD INRA DOCT

National audience

English. Arable agriculture is still highly reliant on herbicides to manage weeds. As part of the necessary shift towards a reduction in pesticide use, the regulatory effect of seed-eating carabid beetles on weeds has received increasing attention in agroecological research. While strong evidence points to carabids exerting a regulatory effect on certain weed species, it is difficult to predict whether a particular assemblage of carabid species will drive the function of weed seed predation in field conditions. We report on specific research actions being conducted within the C-IPM BioAWARE project that focuses on weed regulation by carabid biodiversity. We first present statistical analyses aimed at identifying key assemblages of carabid taxa delivering high weed seed predation of Viola arvensis seeds during spring. Our results suggest that high predation rates occur mainly in simple assemblages of carabid beetles, and underline the possibly functionally complimentary association of Poecilus and Harpalus, two seed-eating carabid genera that show contrasted foraging strategies. We then present the principles and the implementation of the BioAWARE large-scale European survey currently in place. We briefly explain how this large-scale design will be used to identify: (i) key carabid assemblages delivering high seed predation of a large range of weeds; and, (ii) the landscape characteristics that contribute most to support these key assemblages, and thus the service of weed regulation.