Optimization of Operation Parameters for Multi-rotor Plant Protection Unmanned Aerial Vehicle (UAV) Spraying Chlorantraniliprole to Control Spodoptera frugiperda at Different Growth Stages of Maize

【Objective】The effects of operation parameters of multi-rotor plant protection unmanned aerial vehicle (UAV) at different growth stages of maize on deposition quality and the control efficacy of Spodoptera frugiperda were compared to select the optimal operation parameters, with an aim to provide scientific basis for precise pesticide application of S. frugiperda.【Method】DJI T20 six-rotor plant protection UAV was used as the research object, the operation parameters including flight altitude, flight speed and nozzle type were tested for optimization of deposition distribution at the trumpet stage and heading stage of maize, and the population decline rate and control effect of S. frugiperda 7 d after the application of pesticides were investigated.【Result】At trumpet stage of maize, when a SX110015VS nozzle operated at a flight speed of 4 m/s and at a flight altitude of 2.5 m above the maize canopy, the maximum normalized average droplet deposition was 0.45 μL/cm2. When a SX110015VS nozzle operated at a flight speed of 4 m/s and a flight altitude of 1.5 m, both average droplet coverage and average droplet density were the highest, which were 44.92 drops/cm2 and 9.31%, respectively. At heading stage of maize, the normalized average droplet deposition, average droplet coverage and average droplet density were the highest when a SX110015VS nozzle operated at a flight speed of 4 m/s and a flight altitude of 2.5 m, which were 0.50 μL/cm2, 82.92 drops/cm2 and 7.67%, respectively.【Conclusion】The actual occurrence level of pests should be taken into consideration in the selection of operation parameters at trumpet stage and heading stage of maize. The highest droplet deposition was achieved when the UAV flew at a speed of 4 m/s, an altitude of 2.5 m and a nozzle type of SX110015VS, the corrected control efficiency was more than 85% after 7 days of application.