Mosquito control programs are now threatened by the selection of mosquito populations resistant to the chemical insecticides. Thus, alternative vector control methods are necessary. The current study was aimed to study the effects of synergist piperonyl butoxide (PBO) on lambdacyhalothrin tolerance on Anopheles gambiae sensu lato larvae from Toviklin district in Couffo department in south-western Benin, West Africa. Larvae and pupae were collected from April to July 2024 during the great rainy season in Toviklin district. Larval bioassays were performed on these collected Anopheles gambiae s.l. larvae using lambdacyhalothrin as larvicide and piperonyl butoxide (PBO) as enzyme inhibitor or synergist. The results showed that mono-oxygenase enzymes played a role in Anopheles gambiae s.l. larvae tolerance to lambdacyhalothrin in Toviklin district. Synergist PBO contributes to improve the efficacy of insecticide when problems of resistance have arisen.





