Spray coverage, droplet density, and efficacy of drone fungicide applications in corn

Abstract

The use of spray drones in agriculture, particularly for applying fungicides in corn, is advancing rapidly. Therefore, understanding their application performance is important for effective crop management. Studies were conducted to assess spray coverage and droplet density within the corn ( Zea mays L.) canopy at two spray volumes (18.7 and 46.8 L ha ⁻¹ ) using two commercially available spray drones (DJI Agras T30 and T40). For the DJI T30, each spray volume was applied at three different heights of 2.2, 3.0, and 3.8 m above the corn canopy, while for T40, both spray volumes were applied at a fixed height of 2.2 m. Further, fungicide applications were conducted using the DJI T30 drone at two spray volumes, and disease control and corn yield were recorded to assess efficacy. Spray coverage ranged from 0.2% to 3.4%, with high variability observed across the swath and within the corn canopy. Coverage and droplet density increased with spray volume across both drones. Application height did not affect coverage, but its effect on droplet density varied by volume. Both drone types showed comparable coverage, but the DJI T40 (rotary atomizers) had significantly higher droplet density than the DJI T30 (hydraulic nozzles). For fungicide applications, the higher spray volume (46.8 L ha ⁻¹ ) improved disease control in both years. Corn yield was similar across both spray volumes and the untreated control. Overall, the results indicate that spray drones can be a valid tool for timely fungicide applications to support effective disease management in corn production.