Susceptibility of Culex quinquefasciatus larvae to different insecticides

Introduction: This study aimed to assess the susceptibility of Culex quinquefasciatus larvae to two pyrethroids (Cypermethrin and Deltamethrin), two derivatives of Avermectin (Ivermectin and Abamectin) and an organophosphate (Temephos). Methods: Third- and fourth-instar larvae of C. quinquefasciatus were exposed to different concentrations of insecticides (eleven repetitions) according to the World Health Organization's protocol. One hour after exposure, larvae were washed in dechlorinated tap water, transferred to plastic containers containing water without chlorine, fed and observed for periods of 24h until reaching adulthood. To determine lethal concentrations, the obtained values were submitted to regression analysis using the probit model with the Minitab 15 program. Results: The highest concentration used for the LC50 from probit analysis was for Temephos. The evaluated insecticides caused more pronounced larvae mortality in the first 24h with the exception of those exposed to ivermectin. Conclusions: This study demonstrates that larvae are susceptible to all tested insecticides and that there is a need for monitoring the use of insecticides.