Background Space spraying of insecticides is still an important means of controlling Aedes and Culex mosquitoes and arboviral diseases. This study evaluated the space spray efficacy of Fludora Co-Max EW, (water-based insecticide space spray combining flupyradifurone and transfluthrin with film forming aqueous spray technology (FFAST)), against wild insecticide-resistant Aedes aegypti and Culex quinquefasciatus mosquitoes from Abidjan, Côte d’Ivoire, compared with K-Othrine EC (deltamethrin-only product), in small-scale field trials. Methods Wild Ae. aegypti and Cx. quinquefasciatus mosquito larvae were collected in Abidjan, Côte d’Ivoire from August to December 2020. Mosquito larvae were reared in the laboratory until the adult stage. Fludora Co-Max EW and K-Othrine EC were tested against emerged adult females (F0 generation) using ultra-low volume cold fogging (ULV) and thermal fogging (TF) delivery technology, both outdoors and indoors in Agboville, Côte d’Ivoire. Specifically, cages containing 20 mosquitoes each were placed at distances of 10, 25, 50, 75 and 100 m from the spraying line for outdoor spraying, and at ceiling, mid-height and floor levels for indoor house spraying. Knockdown and mortality were recorded at each checkpoint and compared by treatments. Results Overall, Fludora Co-Max EW induced significantly higher knockdown and mortality effects in the wild insecticide-resistant Ae. aegypti and Cx. quinquefasciatus compared with K-Othrine EC. In both species, mortality rates with Fludora Co-Max EW were > 80% (up to 100%) with the ULV spray outdoors at each distance checkpoint (i.e. 10–100 m), and 100% with the ULV and TF sprays indoors at all checkpoints (i.e. ceiling, mid-height and floor). K-Othrine EC induced high mortality indoors (97.9–100%), whereas mortality outdoors rapidly declined in Ae. aegypti from 96.7% (10 m) to 36.7% (100 m) with the ULV spray, and from 85.0% (10 m) to 38.3% (100 m) with the TF spray. Fludora Co-Max EW spray applied as ULV spray outdoors had higher knockdown and higher killing effects on Ae. aegypti and Cx. quinquefasciatus than when applied as TF spray. Fludora Co-Max EW performed better against Cx. quinquefasciatus than against Ae. aegypti. Conclusions Fludora Co-Max EW induced high mortality and knockdown effects against wild insecticide-resistant Ae. aegypti and Cx. quinquefasciatus Abidjan strains and performed better than K-Othrine EC. The presence of flupyradifurone and transfluthrin (with new and independent modes of action) and FFAST technology in the current Fludora Co-Max EW formulation appears to have broadened its killing capacity. Fludora Co-Max EW is thus an effective adulticide and may be a useful tool for Aedes and Culex mosquito and arbovirus control in endemic areas. Graphical Abstract

Background: Space spraying of insecticides is still an important mean of controlling Aedes and Culex mosquitoes and arboviral diseases. This study evaluated the space spray efficacy of Fludora Co-Max EW (a combination of flupyradifurone and transfluthrin, with Film Forming Aqueous Spray Technology (FFAST)) against wild, insecticide-resistant Aedes aegypti and Culex quinquefasciatus populations from Abidjan, Côte d’Ivoire, against K-Othrine EC (deltamethrin-only product), through small-scale field trials. Methods: Wild Ae. aegypti and Cx. quinquefasciatus mosquito larvae were collected in Abidjan, Côte d’Ivoire from August to December 2020. Mosquito larvae were reared until adult stage. Emerged adult females were tested against Fludora Co-Max EW and K-Othrine EC using ultra-low volume cold fogging (ULV) and thermal fogging (TF) both outdoors and indoors in Agboville, Côte d’Ivoire. Cages containing 20 mosquitoes each were placed at 10, 25, 50, 75 and 100 m from the spraying line for outdoor spraying, and at ceiling, mid-height and floor levels for indoor house spraying. Knockdown and mortality were recorded at each checkpoint and compared by treatments.Results: Overall, Fludora Co-Max EW induced significantly higher knockdown and mortality effects in the wild insecticide-resistant Ae. aegypti and Cx. quinquefasciatus compared with K-Othrine EC. With both species, Fludora Co-Max EW mortality rates were above 80% (up to 100%) for outdoor ULV spray at each distance checkpoint (i.e. 10 to 100 m), and 100% for indoor ULV and TF sprays at all level checkpoints (i.e. ceiling, mid-height and floor). K-Othrine EC induced high mortality indoors (97.9-100%), whereas outdoor mortality rapidly declined in Ae. aegypti from 96.7% to 36.7% with ULV, and 85.0% to 38.3% with TF, from 10 to 100 m. For outdoor Fludora Co-Max EW spray, ULV showed both higher knockdown and killing performance Ae. aegypti and Cx. quinquefasciatus compared with TF. Fludora Co-Max EW performed better against Cx. quinquefasciatus compared with Ae. aegypti.Conclusions: Fludora Co-Max EW induced high mortality and knockdown effects against wild insecticide-resistant Ae. aegypti and Cx. quinquefasciatus Abidjan strains and performed better than K-Othrine EC. The presence of flupyradifurone and transfluthrin (with new and independent modes of action) and FFAST technology in the current Fludora Co-Max EW formulation appears to have broadened its killing capacity. Fludora Co-Max EW is thus an effective adulticide and may be a useful tool for Aedes and Culex mosquito and arbovirus control in endemic areas.

Background: Space spraying of insecticides is still an important mean of controlling Aedes and Culex mosquitoes and arboviral diseases. This study evaluated the space spray efficacy of Fludora Co-Max EW (a combination of flupyradifurone and transfluthrin, with Film Forming Aqueous Spray Technology (FFAST)) against wild, insecticide-resistant Aedes aegypti and Culex quinquefasciatus populations from Abidjan, Côte d'Ivoire, against K-Othrine EC (deltamethrin-only product), through small-scale field trials. Methodology: Wild Ae. aegypti and Cx. quinquefasciatus mosquito larvae were collected in Abidjan, Côte d'Ivoire from August to December 2020. Mosquito larvae were reared until adult stage. Emerged adult females were tested against Fludora Co-Max EW and K-Othrine EC using ultra-low volume cold fogging (ULV) and thermal fogging (TF) both outdoors and indoors in Agboville, Côte d'Ivoire. Cages containing 20 mosquitoes each were placed at 10, 25, 50, 75 and 100 m from the spraying line for outdoor spraying, and at ceiling, mid-height and floor levels for indoor house spraying. Knockdown and mortality were recorded at each checkpoint and compared by treatments. Principal findings: Overall, Fludora Co-Max EW induced significantly higher knockdown and mortality effects in the wild insecticide-resistant Ae. aegypti and Cx. quinquefasciatus compared with K-Othrine EC. With both species, Fludora Co-Max EW mortality rates were above 80% (up to 100%) for outdoor ULV spray at each distance checkpoint (i.e. 10 to 100 m), and 100% for indoor ULV and TF sprays at all level checkpoints (i.e. ceiling, mid-height and floor). K-Othrine EC induced high mortality indoors (97.9-100%), whereas outdoor mortality rapidly declined in Ae. aegypti from 96.7% to 36.7% with ULV, and 85.0% to 38.3% with TF, from 10 to 100 m. For outdoor Fludora Co-Max EW spray, ULV showed both higher knockdown and killing performance Ae. aegypti and Cx. quinquefasciatus compared with TF. Fludora Co-Max EW performed better against Cx. quinquefasciatus compared with Ae. aegypti. Conclusion/significance: Fludora Co-Max EW induced high mortality and knockdown effects against wild insecticide-resistant Ae. aegypti and Cx. quinquefasciatus Abidjan strains and performed better than K-Othrine EC. The presence of flupyradifurone and transfluthrin (with new and independent modes of action) and FFAST technology in the current Fludora Co-Max EW formulation appears to have broadened its killing capacity. Fludora Co-Max EW is thus an effective adulticide and may be a useful tool for Aedes and Culex mosquito and arbovirus control in endemic areas.