Bio-efficacy of ultrasound exposure against immature stages of common house mosquitoes under laboratory conditions

Abstract

Purpose: In southern Iran with a tropical climate, the above and underground cisterns of drinking water are the main habitats for immature stages of mosquitoes. The local people do not agree with using calcium hypochlorite granules in the water cisterns due to the change of water taste. Following the increased worldwide interest in using ultrasound technology for water disinfection, this study was conducted to assess the possible dual effects of ultrasound waves against immature mosquitoes.Materials and methods: Combinations of four power levels, two frequencies, three temperatures, and eight exposure times were applied to immature Culex pipiens. The exposure chamber of immature mosquitoes was the disposable cups placed inside a sonication bath containing tap water.Results: The mortality rate of immature mosquitos was 85–91% at 10–25 W, 30 °C and 130 kHz. The most effective ultrasound regimen for causing immature mortality included a fixed frequency of 130 kHz, a temperature of 30 °C, and a power level of 20–25 W. The lowest efficacy was observed in the egg stage. The median lethal time (LT50) and ninety percent lethal time (LT90) of sonication was 5.9 ± 0.6 min and 1.6 ± 0.1 min at 30 °C and a fixed frequency of 130 kHz.Conclusions: Evidence indicated effective ultrasound irradiation against immature mosquitoes in the water. This study provides a clear scientific basis for larvicidal properties induced by ultrasound emissions at laboratory conditions. The findings could be used for setting the ultrasound devices in the field investigations for achieving desired effectiveness.