Can agricultural extension policies be improved by leveraging the power of peer influence? In this study, we evaluate the performance of the French Ecophyto plan aimed at reducing pesticide use, focusing on its flagship scheme, which has provided technical assistance to 3,000 volunteer pilot farms enrolled as peer groups since 2011. We use panel data collected from a representative sample of vineyards, known to be among the heaviest consumers of pesticides. We apply a variety of quasi-experimental approaches to estimate the impact of program participation on pesticide use and crop yields of enrolled vineyards. We find that participants have used 8 to 22 percent lesser pesticides than they would have used in the absence of the program. Moreover, we find that this change of practices resulted in a decrease in yields for only a fraction of enrolled peer farms, while others appear to have maintained their yields. Altogether these results suggest that providing technical assistance to peer groups can be effective in significantly reducing pesticide use in France, and presumably in developed countries more generally, for a cost per hectare that is not greater than that of the average European agri-environmental scheme.