Spray deposition on weeds (Palmer amaranth and Morningglory) from a remotely piloted aerial application system and backpack sprayer

Authors: Martin, Daniel - Dan; SINGH, VIJAY - Virginia Tech; Latheef, Mohamed - Ab; BAGAVATHIANNAN, MUTHU - Texas A&M University

Submitted to: Drones
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/15/2020
Publication Date: 9/19/2020
Citation: Martin, D.E., Singh, V., Latheef, M.A., Bagavathiannan, M.V. 2020. Spray deposition on weeds (Palmer amaranth and Morningglory) from a remotely piloted aerial application system and backpack sprayer. Drones. 4(3):59. https://doi.org/10.3390/drones4030059.
DOI: https://doi.org/10.3390/drones4030059

Interpretive Summary: Post-emergent weeds in major agronomic row crops cause $15B worth of yield loss annually in the United States. This work established the feasibility of using remotely piloted aerial application systems (RPAAS) to replace backpack spray applications. Data showed that RPAAS was able to effectively deposit sprays on plant surfaces, with four times the number of total spray droplets on the undersides of leaves compared to the backpack sprayer. These results show that replacing backpack spray applications with more efficient RPAAS systems will fully maintain required deposition rates of weed control products.

Technical Abstract: This study was designed to determine whether a remotely piloted aerial application system (RPAAS) could be used in lieu of a backpack sprayer for post-emergence herbicide application. Consequent to this objective, a spray mixture of tap water and fluorescent dye was applied on Palmer amaranth and ivyleaf morningglory using an RPAAS at 18.7 and 37.4 L ha-1 and a CO2 - pressurized backpack sprayer at 140 L ha-1 spray application rates. Spray efficiency (the proportion of applied spray collected on an artificial sampler) for the RPAAS treatments was comparable to that for the backpack sprayer. Fluorescent spray droplet density was significantly higher in the adaxial surface for the backpack sprayer treatment than that for the RPAAS platforms. The percent of spray droplets on the abaxial surface for the RPAAS aircraft at 37.4 L ha-1 was 4-fold greater than that for the backpack sprayer at 140 L ha-1. The increased spray deposition on the abaxial leaf surfaces was likely caused by rotor downwash and wind turbulence generated by the RPAAS which caused leaf fluttering. This improved spray deposition may help increase the efficacy of contact herbicides. Test results indicated that RPAASs may be used for herbicide application in lieu of conventional backpack sprayers.