Comparison of spray drift between spraying drone and conventional airblast sprayer in vineyards

Spraying Unmanned Aerial Vehicles (UAVs) are autonomous airborne platforms that primarily operate on predetermined flight plans and spraying missions. Although spraying UAVs are increasingly used for plant protection in vineyards, limited experimental evidence exists on how operational parameters influence spray drift under real field conditions, especially in European vineyards. This study quantified ground-level drift from a UAV sprayer in a commercial vineyard, evaluating two flight altitudes (2.0 m and 2.5 m AGL), two flight speeds (1.0 and 1.5 m/s), and three application strategies (inter-row with and without a buffer line, and over-row with a buffer line). An additional set of replicates using a conventional air-assisted sprayer was included as a reference for current vineyard practice. Spray drift was measured at multiple downwind distances using filter paper collectors and analysed with laboratory spectrophotometric methods following ISO 22866. Drift from UAV applications was highly concentrated near the field boundary and declined sharply within the first 5 m for all configurations. Flight altitude was the dominant driver: increasing AGL from 2.0 m to 2.5 m raised drift at the closest sampling point by 30–70%. Higher flight speed (1.5 m/s) increased drift by 10–20% compared with 1.0 m/s. Applying a buffer reduced drift by up to 60%, particularly in inter-row spraying. Under optimal UAV settings (2.0 m AGL, 1.0 m/s, buffer applied), drift became negligible beyond 10 m downwind. Compared with the conventional air-assisted sprayer, UAV applications under optimised conditions reduced drift at the closest sampling distance by approximately 65–70% and showed substantially lower drift beyond 10 m. These findings demonstrate that appropriate UAV operational settings can significantly reduce off-target movement and offer a lower-drift alternative to conventional terrestrial sprayers in vineyard applications and such mitigation strategies should always be considered prior to designing a flight plan or spray mission.