Effect of three types of spray adjuvants on the distribution of spray droplet deposition in hilly citrus under precise fruit tree operation mode of unmanned aerial vehicles

To clarify the effect of aerial spray on hilly citrus orchards when applying unmanned aerial vehicles (UAV) under the precision fruit tree operation mode, three types of spray adjuvants (vegetable oil adjuvant Beidatong, non-ionic surfactant adjuvant Y-20079 and silicone adjuvant 806) were studied. The results showed that comparing with the control check (CK), different types of adjuvants and different concentration of the same adjuvant have different effects on droplet density, coverage and deposition under the same operation parameter. Among them, the result of adding Beidationg with a 1.0% volume fraction was significantly superior to that of 0.5% volume fraction, which could increase the maximum droplet density, coverage and deposition amount by 42.0%, 92.3% and 33.6%, respectively; the result of adding Y-20079 with a 1.0% volume fraction was significantly superior to that of 0.5% volume fraction, which could increase the maximum droplet density, coverage and deposition amount by 101.0%, 86.5% and 36.0%, respectively; the result of adding 806 with a 0.5% volume fraction was significantly superior to that of 0.25% volume fraction, which could increase the maximum droplet density, coverage and deposition amount by 43.9%, 76.0% and 35.0%. respectively. After adding adjuvants, the penetration rate of the test solution to the upper and lower parts of the citrus canopy can be increased by 10.2%-41.5% and 4.0%-42.0% (Beidatong), 101.0% and 7.3%-78.7% (Y-20079), 10.2%-43.9% and 41.3% (806). Compared with the control check, the deposition of pesticides in the canopy projection area was reduced by 38.2%-48.5% (Beidatong), 10.1%-46.3% (Y-20079) and 42.1%-56.2% (806). Comparing with the control check, the amount of pesticide deposition in the blank area between adjacent plants incresed by the addition of Beidatong (3.7%-39.3%), Y-20079 (7.0%-50.9%), and 806 (22.3%-41.4%). The results of the research showed that when applying precise aerial spraying to mountain and citrus orchards, adding a volume fraction of 1.0% Beidatong, 1.0% Y-20079, or 0.5% 806 in the spray solution can effectively improve the application on the canopy of the hilly citrus.