Operational evaluation of unmanned aerial vehicle-applied granular larvicides in an integrated mosquito management...

While unmanned aerial vehicles (UAVs) offer substantial benefits to integrated mosquito management (IMM) programs, the novelty of the technology presents challenges regarding how to best incorporate it into a control regimen. Here, larval assays, semi-field deposition and efficacy trials, and field trials guided by light detection and ranging (LiDAR) data, were conducted with two granular larvicides, Altosid® XR-G and VectoBac® G. Results from the larval assays demonstrated inherent efficacy of the larvicides, with Altosid® XR-G's LD₉₀ value corresponding to approximately mid-label application rates, and one fourth the lowest application rate of VectoBac® G resulting in 94.4% mortality at 24 h. Deposition studies established that increases in flight altitude resulted in significant decreases in larvicide reaching dispersed larval inhabiting sites for both Altosid® XR-G (p = 0.01) and VectoBac® G (p = 0.046). Semi-field efficacy trials resulted in mortality rates of 69.46% for VectoBac® G and 53.22% for Altosid® XR-G. Following a modified Before-After Control-Impact (BACI) study design, 22 weeks of consecutive adult trapping, and 12 concurrent weeks of larval surveys and landing rate counts, indicated that applications of larvicide had no significant impact on mosquito population abundances. These results demonstrate the importance of evaluating UAV based applications on a local level, as habitat type, flight altitude, and environmental conditions likely impact treatment efficacy. Results also underscore the need for continued evaluations of UAV-based insecticide applications to better inform IMM practitioners on the benefits and limitations of UAV technology.