Comparison of the physical spray efficacy between unmanned helicopter and motorized knapsack sprayer in Thai paddy field

The physical spray efficacy was compared between unmanned helicopter and motorized knapsack sprayer for the application of pesticide in rice paddy field in Thailand. The unmanned helicopter treatment resulted in a significantly higher number of droplet density than that of the motorized knapsack sprayer treatment. In addition, droplet deposition did not differ between the two spraying techniques on the top and panicle positions. However, droplet deposition on the bottom position from the unmanned helicopter was higher than that from the motorized knapsack sprayer. The unmanned helicopter effectively reduced droplet losses to the ground compared with that of the motorized knapsack sprayer. With respect to droplet drift from sprayed area, the distance achieved by the unmanned helicopter was 3 m greater than that by the motorized knapsack sprayer. These results suggest that the efficacy of the unmanned helicopter was similar or greater than that of the motorized knapsack sprayer. Overall, we found that unmanned aerial vehicles improved performance and enabled rational pesticide application rice production in Thailand.