Uncrewed Aerial Spray Systems For Mosquito Control: Efficacy Studies For Space Sprays

Achieving an appropriate droplet size distribution for adulticiding has proved problematic for unmanned aerial spray systems (UASSs). The high-pressure pumping systems utilized on crewed aircraft conflict with the weight constraints of UASSs. 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 a UASS was calibrated to discharge an appropriate droplet size distribution (Dv0.5 of 48 µm and 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 1 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.