Behavioural Ecology of Weed Regulation by Carabid Beetles

As part of the ECOPHYTO 2018 and EU targets for reducing herbicides while maintaining weed control, this PhD will examine some of the ecological mechanisms underlying carabid predation of weed seeds and the ensuing regulation of weed populations.

The broad goals of the UMR Agroécologie are to better understand agro-ecological processes so that we can develop sustainable management solutions, which reduce pesticide inputs and support a durable, intensive agriculture. In a recent paper, Bohan et al. (2011) demonstrated that carabid beetles appear to regulate the seedbank of weed species in-field. This pattern was national in scale and had all the necessary hallmarks of a valid, working « Ecosystem Service ». Bohan et al. (2011) conjectured that this naturally present service might be used to replace some herbicide applications for long-term sustainable weed control, which could support long-term goals (eg ECOPHYTO 2018) to reduce herbicide inputs while maintaining weed control.

This PhD will test part of this conjecture. We hypothesise that foraging patterns and seedbank regulation are intimately linked to: carabid behaviour; past exposure to weed seeds; and, the spatio-temporal distribution of weeds in the field (Harrison & Gallandt 2012). This project will test these expectations using a combination of: i) video experiments of carabid foraging and feeding behaviour at UMR Agroécologie (Guy et al. 2008); ii) mesocosm and field experiments (Smith 2007) to manipulate weed seed distribution patterns in ways designed to manipulate predation; and, iii) field experiments and data analysis to search for general changes in the weed seedbank (fitness) with weed (patch) density and carabid abundance and diversity.