Broadcasting of tiny granules by drone to mimic liquid spraying for the control of fall armyworm (Spodoptera frugiperda)

Abstract BACKGROUND The fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith), is an invasive pest. Maize is one of its preferred host plants. The traditional application of granules has been effective for the control of FAW. Nevertheless, the challenge is to develop an application method that is less labor‐intensive and also efficient. RESULTS Tiny granules in the size range of 0.38–0.55 mm were prepared by the centrifugal granulation method for drone application. The in‐swath distribution patterns of granules deposited on sticky tapes were similar to the distribution of aqueous droplets through drone spraying. In the range of 1.5–3.5 m, a relatively higher aircraft height of flight can provide a more uniform distribution pattern of deposited granules, but resulted in less deposit of tiny granules in the whorl of maize plants. Similarly, the deposit of granules in the whorl of maize plants significantly decreased when the flight speed increased from 4 to 6 m s −1 . Granules gathered in the whorl accounted for 50.8–58.7% of total granules deposited in the maize canopy. The field experiment demonstrates granular formulations (containing 0.25% chlorantraniliprole + 0.15% emamectin benzoate, or higher concentrations) can provide better and longer duration of FAW control than the aqueous spray formulation at the whorl stage of maize plants. CONCLUSION Broadcasting of tiny granules by drone can provide better FAW control than liquid spray. The architecture of the maize plant and the downward airstream of the drone create favorable conditions for the deposition of granules in whorls. © 2021 Society of Chemical Industry.