Abstract:

To investigate the effects of different operational parameters of plant protection unmanned aerial vehicle（UAV）on the control efficacy against rice planthoppers，field trials were conducted during the booting stage of early-season rice and the tillering stage of late-season rice in Jinhua City，Zhejiang Province，China. The effects of spray volume，operating height，and flight speed on control efficacy were analyzed. The results showed that spray volume was the primary factor affecting the control efficacy of UAV. At the booting stage，increasing spray volume from 2 L to 4 L per 667 m2 improved the control efficacy by 19.95-25.59 percentage points；at the tillering stage，a spray volume of 3 L per 667 m2 was sufficient to achieve the optimal control efficacy. The effect of operating height on control efficacy varied with growth stage：at the booting stage，operating heights of 2-3 m provided relatively stable control efficacy；at the tillering stage，increasing operating height from 2 m to 4 m resulted in considerable differences in control efficacy. Flight speeds of 4 m·s^-1 and 5 m·s^-1 showed no significant difference in control efficacy. Under appropriate operational parameters，UAV application achieved control efficacy comparable to that of knapsack electric sprayer，with no adverse effects on rice growth. In conclusion，the recommended operational parameters for UAV application at the tillering stage of rice are operating height of 2 m，spray volume of 3 L per 667 m2，and flight speed of 4 m·s^-1；at the booting stage，the recommended parameters are operating height of 2-3 m，spray volume of 4 L per 667 m2，and flight speed of 4-5 m·s^-1.

Key words: unmanned aerial vehicle, operational parameters, rice planthoppers, rice, control efficacy