Social learning and diffusion of innovations through peers can be a key component of the agroecological transition, as it contributes to the generalization of good practices and improves the efficiency of public policies by increasing the number of farmers reached without additional cost. We evaluated the spillover effects of a pesticide reduction scheme implemented in France during the 2010s, which was designed to train farmers in pesticide-saving farming practices and encourage knowledge diffusion beyond the scope of farms enrolled in the program. We applied a quasi-experimental approach to pseudo-panel data collected at national scale and found that doubling the proportion of participants would reduce pesticide use by about 10% within representative cohorts on average. Besides, we found an additional effect of similar magnitude on farms that report having participated to demonstration visits to the farms trained by the program. These results suggest that agricultural training programs are likely to generate spillover effects at lower cost.