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Abstract.

Most orchards in China are traditionally horticultural dense plantations, with irregular plantings and narrow row spacing. During the period of growth, with the expansion of canopies, the branches and leaves of trees seriously overlap, which results in canopy closure. This may cause great difficulties to control diseases and insect pests regarding fruit trees. In this paper, in order to explore the adaptability and application prospect of unmanned aerial vehicle (UAV) for plant-protection in traditional closed orchards in China, field spraying tests were conducted and ten-year-old apple trees with fruits were utilized as spray targets. A Z-3N single-rotor UAV and a 3WWDZ-10 six-rotor UAV were selected as research objects and have a comparison with an air-assisted sprayer. The results showed that compared with the air-assisted sprayer, the UAV application saved up to 97.2% of the solution, and effectively improved pesticide utilization ratios and working efficiency. In terms of the air-assisted sprayer, the droplet deposition at the lower parts of trees was higher than the upper parts due to radial spray patterns, whereas the UAV had an opposite trend. From the perspective of depositing penetrations, the single-rotor UAV was the strongest with the coefficient of variation of 3.62% and the air-assisted sprayer was the second with the coefficient of variation of 4.71%. The six-rotor UAV was the smallest, with the number of 40.77%. The results offer a reference for the performance optimization of both UAVs and fruit growers to choose suitable plant-protection machinery.