Uncrewed aerial spray systems for mosquito control: Efficacy studies for space sprays

Authors: BONDS, JANE - Bonds Consulting Group; THISTLE, HAROLD - Teals, Llc; Fritz, Bradley - Brad; REYNOLDS, WILLIAM - Leading Edge Associates; KIMBELL, PIPER - Leading Edge Associates

Submitted to: Journal of the American Mosquito Control Association
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/3/2023
Publication Date: 12/30/2023
Citation: Bonds, J.A., Thistle, H., Fritz, B.K., Reynolds, W., Kimbell, P. 2023. Uncrewed aerial spray systems for mosquito control: Efficacy studies for space sprays. Journal of the American Mosquito Control Association. 39(4):223-230. https://doi.org/10.2987/23-7140.
DOI: https://doi.org/10.2987/23-7140

Interpretive Summary: Using unmanned aerial spray systems (UASS) for adulticiding focused on mosquito control is gaining attention, yet there's a knowledge gap regarding achieving the proper droplet size distribution for efficacy. A lightweight rotary atomizer for UASS was calibrated to release a specific droplet size from a designated altitude, and spray distribution, effectiveness, and deposition on the ground were assessed. The results showed that control was feasible across distances of 100-150 meters, though with a ground deposition rate of 13-36% of the total application rate. Additionally, while the spray deposition aligned well with mortality data, further research is crucial to better understand the spray atomization system and to optimize the altitude-droplet size interactions to ensure minimal ground residue. This work established a foundation for the use of UASS in adulticiding and provides direction for improving a systems efficiency and efficacy while ensuring environmental safety.

Technical Abstract: Achieving an appropriate droplet size distribution for adulticiding has proved problematic for unmanned aerial spray systems (UASS). The high-pressure pumping systems utilized on crewed aircraft conflict with the weight constraints of UASS. The alternative is a lightweight rotary atomizer, which when run at a maximum rpm with a minimal flow rate, can achieve the appropriate droplet size distribution. For this study the UASS was calibrated to discharge an appropriate droplet size distribution (Dv0.5 45 µm and a Dv0.9 of 76 µm). Spray was released from an altitude of 23 m (75 ft). The spray plume was shown to effectively disperse through the sampling zone. To achieve the appropriate application rate, the flight speed was 3 m/sec (6.7 mph) with an assumed swath of 150 m (500 ft). The objective of this project was not to conduct an operational application, instead only one flight line was used so that the effective swath width could be confirmed and the appropriate flightline separation defined. This study showed that control was achieved across distances of 100-150 m. Considering a swath width of 150 m (500 ft), ground deposition was 13-36 % of applied material. Spray deposition corresponded well with the mortality data which helped improve confidence in the data. The overall conclusion from this study is that aerial adulticiding is feasible with the system presented here. Further work is required to improve the atomization system to allow operational flight speeds, and to determine the interaction between release altitude and droplet size in order to minimize ground deposition of application material.