Experimental Investigation of Drone-Based Insecticide Application for Effective Pest Management in Groundnut Field Crop

Multi-rotor unmanned aerial vehicles (UAVs) have recently emerged as a leading technology for crop spraying, with significant attention from researchers and manufacturers focused on the performance of battery-powered hexacopter UAVs. The UAV-spraying is influenced by several factors including drone design, configuration, capabilities, operating parameters and crop type. Therefore, in this study, a six-rotor UAV sprayer was experimentally investigated to characterize spray droplets and its effectiveness in a groundnut research field. Chlorantraniliprole insecticide (18.5% SC) was applied at concentrations of 0.10%, 0.15%, 0.20%, and 0.25% using the UAV sprayer. The UAV sprayer was operated under optimized conditions, with a forward speed of 3.0 m s-1, a spray height of 1.0 m, and a pump discharge rate of 1.6 L min-1. An effective spray width of 2.5 m was found during the spraying experiments. Spray droplet samples were analyzed, revealing an actual spray deposition rate of 0.89 μL cm-2 in the upper layer and 0.72 μL cm-2 in the bottom layer of the canopy. Compared to a manual knapsack sprayer (upper layer: 1.34 μL cm-2; bottom layer: 0.32 μL cm-2), the UAV sprayer achieved more uniform coverage in both layers, with 7.43% and 6.32% spray coverage per unit area in the upper and bottom layers, respectively, compared to 9.49% and 3.18% for the manual method. The biological efficacy in controlling leaf folder insect on groundnut was 85.0% to 90.0%. The theoretical and actual application rates of the UAV sprayer were 49.0 L ha-1 and 47.0 L ha-1, respectively. The cost of operation for groundnut crop using a UAV sprayer has been estimated as 350 Rs ha-1 (770 Rs h-1 i.e., 9.2 USD h-1). The powerful downwash airflow generated by the UAV’s propellers enhanced uniform droplet deposition, spray coverage, and area coverage compared to the knapsack sprayer. These findings demonstrated the potential of multi-rotor UAVs for efficient insecticide application in small-scale groundnut farming, providing valuable insights for improving UAV-based crop spraying techniques.