Efficacy of insecticides applied on indoor residual spraying against wild populations of Mansonia humeralis Dyar e Knab, 1916 (Diptera, Culicidae) in western Amazonia

Abstract

Mosquitoes of the subgenus Mansonia are widely distributed in Amazonian environments and may cause considerable nuisance to humans and domestic animals in areas of high population density. This study evaluated the efficacy of intradomiciliary residual spraying (IRS) as a protective measure against wild populations of Mansonia humeralis under simulated field conditions. Etofenprox, alpha-cypermethrin, and bendiocarb were applied to different wall substrates: painted cement, unpainted cement, brick, painted wood, and unpainted wood. Insecticide performance was assessed based on knockdown at 60 min of exposure and female mortality at 24 h, with repetitions in the intervals of 7, 30, 60, and 90 days post-application for alpha-cypermethrin and bendiocarb, and up to 120 days for etofenprox. The satisfactory knockdown effect (> 80%) was short-lived, lasting up to 7 days after application, especially on surfaces treated with alpha-cypermethrin and bendiocarb. Higher mortality rates were observed on wooden surfaces, particularly unpainted wood, which also exhibited greater residual activity. A general decline in mortality was detected after 60 days for all insecticides and substrates; however, etofenprox maintained residual efficacy up to 120 days post-application. Generalized linear mixed models (GLMM) showed significant effects of substrate type (p < 0.001), especially painted and unpainted wood, and exposure time (p < 0.001) on mosquito mortality. These findings suggest that IRS with the evaluated insecticides may contribute to the control of Ma. humeralis, with improved performance on wooden substrates. Nevertheless, further studies under field conditions and over extended evaluation periods are required before definitive recommendations can be made.