Switzerland was the first European country to approve the use of unmanned aerial vehicles (UAVs) for the purpose of plant protection treatments. The regulatory framework that has been established requires UAV sprayers to undergo a series of technical assessments that have generated a substantial amount of data. Here, we first describe the regulatory framework and the underlying rationales, followed by analyzing data from the technical assessments. The results show that the UAV sprayers being used in Switzerland achieve homogeneous transversal spray liquid distributions with coefficients of variation below 15 % at effective swath widths that are typically lower than those indicated by UAV manufacturers. Moreover, the lateral wind generated by the UAV sprayers as measured at distances of 10 m and 20 m, respectively, is not substantially affected by UAV size or weight. A survey we conducted to gain insight into agricultural practices under the current regulatory framework suggests that up to 11.5 % of the total of Swiss vineyards were treated with UAV sprayers in 2023. Other uses, such as spreading slug pellets, seem to gain importance as well. Finally, efficacy trials performed in Swiss vineyards suggest that UAV sprayers achieve limited control efficacy of powdery and downy mildew at high disease pressure, which is likely to be due to the relatively low amount of deposit around and on the bunches. We conclude this paper by outlining future regulatory challenges and directions for further development.
