Abstract

The application of unmanned aerial vehicles (UAVs) in viticulture is becoming increasingly popular. To the best of our knowledge, there are no studies comparing the effects of UAV spraying to manual spraying in high-slope vineyards. The goal of this study was to evaluate the effects of UAV spraying on droplet average diameter, droplet area percentage, and droplet density for vines grown using vertical shoot positioning (VSP) and Y-shaped trellis systems and to compare them with the effects of manual spraying via an electric knapsack sprayer. The results showed that manual spraying led to the greatest area of droplets for the VSP trellis system, and the uniformity and penetration of droplets with the UAV spraying method were higher than those for manual spraying for this trellis system. Regarding the Y-shaped trellis system, the UAV spraying method yielded lower droplet diameters, higher droplet density, and better uniformity and penetration than manual spraying. Moreover, conducting UAV spraying twice showed no statistical differences in droplet area percentage compared to manual spraying, and the effect of UAV spraying even once was similar to that of manual spraying on the abaxial sides of the leaves in this respect. Our research indicates that UAV spraying was not very suitable for VSP trellis systems, but it could be a good alternative for Y-shaped trellis systems since it is safe and cost-effective by reducing labor, time, and the dosages of the solutions applied. © 2025 by the authors.