Objective: to study the effect of water extraction and renewal on the residual action of temephos applied at 1ppm to cement water-storage containers at home. Methods: the study was conducted in two stages: one, determination of the granular temephos effectiveness on wild Aedes aegypti populations in order to set the monitoring baseline; and second, the measurement of the mean rate of water extraction at home and its effect on the residual activity of temephos. Results: the effectiveness of granular temephos was CL95= 0.095 ppm (IC95 %: 0.079-0.118). As average, it was found that 69.2 % of water stored in cement containers was daily used and renewed, which means significant dilution. For the purpose of simplifying the experiments on residual activity, water was extracted and renewed at a rate of 50 % every day for 2 weeks. It was found that temephos effectiveness significantly declined from day 7 on after application. Conclusions: this rate of water extraction under study has an important effect on the residual activity of temephos. If this rate and the CL95 of granular temephos are considered in estimating the dosing, positive effects on the control of Aedes aegypti and more likely on the occurrence of resistance will be attained.

Objetivo: investigar en qué medida la actividad residual del temefos aplicado a 1 ppm en tanques de cemento domiciliares es afectada por la extracción y reposición de agua derivada de las actividades diarias en el hogar. Métodos: el estudio se realizó en 2 etapas: primero la determinación de la efectividad del temefos granular en poblaciones silvestres de Aedes aegypti para establecer una línea basal de monitoreo y, segundo, la medición de la tasa media de extracción de agua domiciliar y su efecto sobre la residualidad de temefos. Resultados: la efectividad del temefos granular fue de CL95= 0,095 ppm (IC95 %: 0,079 0,118). Se encontró que, en promedio, se usa y repone diariamente el 69,2 % del agua almacenada en tanques de cemento, lo cual indica dilución significativa. Para simplificar los experimentos de residualidad se extrajo y repuso el agua a una tasa de 50 % diaria durante 2 semanas, encontrándose que la efectividad del temefos disminuye significativamente a partir del día 7 de su aplicación. Conclusiones: la extracción de agua a la tasa encontrada tiene efectos importantes en la residualidad de temefos. Si se considerara esta tasa de extracción de agua y la CL95 del temefos granular en el cálculo de su dosificación, se tendrían efectos positivos en el control de Aedes aegypti y muy posiblemente en la aparición de resistencia.

In this paper, we assessed the suitability of using the neonicotinoid imidacloprid with standard ovitraps by evaluating the ovicidal properties of imidacloprid and its influence on the oviposition response of gravid females of Aedes (Stegomyia) aegypti Linnaeus (Diptera: Culicidae). First, we calculated the imidacloprid lethal dose 99 (LD99) by exposing third instar larvae of the target species to different concentrations of the insecticide. Next, Ae. aegypti eggs were exposed to the imidacloprid LD99 for 24 h and hatching inhibition was recorded. Finally, we investigated any potential repellent effect of the imidacloprid solution on the oviposition response of gravid Aedes females in field and laboratory conditions. The LD99 obtained from larvae tests proved to be sufficient to keep any exposed eggs from hatching. No repellent effect was observed; females laid as many eggs in imidacloprid-treated ovitraps as in traps containing either clean water or temephos-treated water in both field and laboratory conditions. Our results indicate that imidacloprid is a suitable insecticide for treating ovitraps against Ae. aegypti.