Assessing the application of spot spray in Nanguo pear orchards: Effect of nozzle type, spray volume rate and adjuvant

Aerial spray is one of the most important applications of unmanned aerial vehicles (UAVs) in agriculture. This work aimed to promote the use of UAVs as an alternative to knapsack electric sprayers in pesticide application in Nanguo pear orchards planted in mountain terraced orchard scenarios. The spray deposition of four types of nozzles (SX110015, XR80015, IDK90015 and TR80015), two spray volume rates (45 and 90 L ha-1 ) and with or without a commercial surfactant adjuvant were evaluated based on the spot spray mode.The air- assisted IDK90015 nozzle showed significantly higher deposition and penetration, and its large droplet size also reduced the risk of drift. Increasing the spray volume rate can increase the amount of droplets deposition. The adjuvant showed excellent potential to improve spray technology in Nanguo pear trees, with a mean deposition of 0.175-0.574 μL cm-2 and penetration of 3.09-66.73%. The droplet size also increased significantly, with volume median diameter (DV0.5 ) of 469 μm.The nozzle type, spray volume rate and adjuvant should be well considered when using the spot spray in orchard. Compared with increasing spray volume rate, the use of air-induction nozzles and surfactant-based adjuvants can improve the spray deposition better. © 2022 Society of Chemical Industry.