Impact of Application Rate and Spray Nozzle on Droplet Distribution on Watermelon Crops Using an Unmanned Aerial Vehicle

Watermelon is one of the most commonly grown vegetable crops worldwide due to the economic and nutritional importance of its fruits. The yield and quality of watermelon fruits are affected by constant attacks from pests, diseases, and weeds throughout all phenological stages of the crop. Labor shortages and unevenness of pesticide applications using backpack and tractor sprayers are significant challenges. The objective of this study was to evaluate the effect of different spray nozzles (XR110015 and MGA60015) and application rates (8, 12, and 16 L ha −1 ) on droplet distribution on different targets in watermelon plants using an unmanned aerial vehicle. Water-sensitive papers were used as targets to analyze the droplet coverage, deposition, density, and volume median diameter. Data were collected from targets placed on the leaf adaxial and abaxial sides, fruit, apical bud, and stem of each plant. The mean droplet coverage and density increased as the application rate was increased, with no significant interaction between the factors or statistical difference between spray nozzles, except for the leaf abaxial side. No significant differences were found for the variables analyzed at application rates of 12 and 16 L ha −1 , whereas significant differences were observed at 8 L ha −1 . The use of unmanned aerial vehicles in watermelon crops is efficient; however, further studies should be conducted to evaluate their effectiveness in pest control and compare them with other application methods.