Unmanned aerial sprayers: Evaluating platform configurations and flight patterns for effective chemical applications in modern vineyards

Authors: Schrader, Mark; BHALEKAR, DATTATRAY - Washington State University; SAHNI, RAMESH - Central Institute Of Agricultural Engineering; KHOT, LAV - Washington State University

Submitted to: Smart Agricultural Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/19/2025
Publication Date: 5/20/2025
Citation: Schrader, M.J., Bhalekar, D.G., Sahni, R., Khot, L.R. 2025. Unmanned aerial sprayers: Evaluating platform configurations and flight patterns for effective chemical applications in modern vineyards. Smart Agricultural Technology. 11. Article 101033. https://doi.org/10.1016/j.atech.2025.101033.
DOI: https://doi.org/10.1016/j.atech.2025.101033

Interpretive Summary: Drones are being used to apply pesticides in vineyards in Washington State. This can be useful as it allows farmers to control pests in hard-to-reach areas and it reduces the likelihood of human exposure. However, drones are limited to spraying only above the canopy, which reduces the amount of pesticide spray that reaches the lower canopy. The lower canopy also tends to be where diseases survive best. We conducted two tests with existing drones to improve spray delivery to the lower canopy. First, we flew the drone across the vineyard rows to compare against flying the drone along the vineyard rows. There wasn’t a noticeable difference in spray coverage between the two flight patterns, but when flying across the rows, there was too much spray on the ground. In the second test, we flew a drone with nozzles angled toward the canopy. When compared to a drone with nozzles facing down, there wasn’t a noticeable difference in spray coverage. Additional engineering is required to make drone pesticide applications more efficient.

Technical Abstract: Unmanned Aerial Sprayers (UASs) are being sought after as a possible alternative to knapsack sprayers in topographically challenging vineyards. However, prior work has identified that UASs have issues with delivering adequate spray mix to the bottom canopy zones. This study was thus conducted to understand and potentially improve spray delivery to the grapevine bottom canopy zones through two flight patterns (cross-row and row-aligned) and three commercial UASs platform configurations (AGRAS T20, AGRAS T30 and AGRAS T30 ‘orchard configuration’, DJI Technology Co.). Three flights were conducted for each treatment at an application rate of 120 L ha-1 (12.83 GPA) over independent replicate test blocks. All tests were conducted in a vertical shoot position (VSP) trained vineyard (cv. Chardonnay). Water sensitive paper and mylar cards were used to quantify coverage (%) and deposition (ng cm-2), respectively. Overall, cross-row flight applications (coverage: 6.70 ± 1.38% [mean ± standard error], deposition: 104.54 ±17.71 ng cm-2) failed to provide significantly different (p>0.05) spray delivery as compared to the row-aligned operations (coverage: 10.10 ± 2.14%, deposition: 83.81±11.17 ng cm-2). Similarly, coverage and deposition data collected for the three UAS geometries failed to present significant differences (p>0.05). Regardless of configuration or flight pattern, the bottom canopy zone received significantly lower deposition than the top canopy zone across treatments. Further engineering towards optimization of UAS geometry is needed for efficient chemical application in modern VSP trained vineyards.