Evaluation of the efficacy of commercially formulated aerosol based pyrethroid insecticides against Culex species (Diptera: Culicidae)

Abstract

Efforts to control mosquito borne diseases of serious public concern rely largely on the control of vectors using pyrethroids. Emergence of insecticide resistance makes control as well as choice of ideal insecticide difficult. Following standard guidelines effectiveness of twelve (12) commercially formulated aerosol insecticides against Culex species in Kano metropolis, Nigeria was evaluated for knockdown and mortality effect in a Peet-Grady chamber. Highest knockdown efficacy was observed with aerosol insecticide coded K11 containing; transfluthrin 0.15% and permethrin 0.23%, having KT₅₀ of 3.7 ± 0.1 and KT₉₅ of 10.0 ± 0.2 mins, which differ significantly (P<0.05) with aerosol F6, aerosol H8 and aerosol J10. All insecticides with the exception of A1 expressed acceptable limit of mortalities (≥90) for effective aerosol insecticide. This study revealed that; number of active ingredients did not affect formulation performance. Permethrin and Transfluthrin were identified as the most effective pyrethroid isomers in the control of Culex mosquitoes. This study further revealed the susceptibility of Culex species of Kano metropolis to aerosol based pyrethroid insecticides. However, significantly low knockdown effect observed in some of the insecticides, suggests knockdown resistance (kdr) in the population of the tested mosquitoes. Constant monitoring of susceptibility status of other mosquito genera is recommended to address challenges that may face the control of mosquito borne diseases.