Efficacy of water- and oil-based mosquito control formulated products evaluated against mosquitoes in a novel compact wind tunnel

Abstract

Insecticides are important tools in an integrated mosquito management program to protect public health from vector-borne disease. Mosquito control programs (MCP) often use adulticides for targeted control. However, mosquitoes can develop resistance to active ingredients (AI) in formulated products (FP), thereby reducing efficacy. Biomist® 3+15 (hereafter, Biomist®) is widely used throughout North Carolina, though previous insecticide resistance (IR) testing identified resistance in some mosquito populations. Some FP are offered with either oil- or water-based options to offer greater flexibility and suit different operational needs. Duet® (oil-based) and AquaDuet® (water-based) contain the same dual action AI (sumithrin and prallethrin). Further testing is needed to identify potential differences in efficacy for FP with different diluents. Laboratory and wild Aedes albopictus, Culex quinquefasciatus, and Culex pipiens/quinquefasciatus were exposed to aerosolized Biomist® (AI: permethrin), Duet® (AI: prallethrin, sumithrin), AquaDuet® (AI: prallethrin, sumithrin), or air (control) for 10 s in a novel compact wind tunnel. Knockdown was measured at 2 h post-exposure and mortality was measured at 24 h and 48 h post-exposure. Resistance or susceptibility status was determined based on mortality at the final time point. Chi square tests (P<0.001) showed significant differences in efficacy of oil- and water-based FP and FP resistance between Culex populations. In lab Culex, Duet® caused significantly higher mortality than AquaDuet®, though Biomist® caused significantly higher mortality than Duet®. In wild Culex, Duet® caused significantly higher mortality than AquaDuet®, while Biomist® caused significantly higher mortality than both Duet® and AquaDuet®. Wild Culex exhibited significantly higher rates of resistance to all three FP compared to lab Culex. No significant differences in mortality between FP were identified when lab and wild Aedes were compared. Different FP may be useful for different MCP needs. However, efficacy of oil- and water-based FP may vary between different mosquito populations, and this should be evaluated before widespread use. These results highlight the importance of mosquito surveillance efforts and ongoing IR testing to guide FP selection to maximize efficacy of targeted control.