The Ecophyto plan is a high stake program implemented in France since 2008 with the aim to halve pesticides use in the farming sector in 10 years. The main disposal of the program is the dephy network. It consists in providing technical assistance to groups of volunteer farms. The French government is currently trying to scale-up the program, which calls for the evaluation of its impacts on pesticide use and yields. Coupling Dephy data and national surveys from 2010 to 2016, we use a slate of quasi-experimental approaches - Matching, Difference-in-difference matching, and Difference-in-difference - to estimate the impact of participation in the program on pesticide use and crop yields on enrolled vineyards. We find that participants have achieved reductions in pesticide use that ranges from 10~to 30~percent, thanks to the program. We moreover find that the reduction in the use of chemicals was accompanied by an increase in the use of biocontrol products. Finally, we find that this change of practices resulted in a reduction in yields for only a fraction of enrolled farms. Our study provides new evidence regarding the effectiveness of technical assistance alone in reducing pesticide use among French farmers, and presumably among farmers in developed countries more generally. It shed lights on potential beneficial impacts as well as warnings of the effects of such programs.