Susceptibility of Anopheles gambiae complex mosquitoes to microbial larvicides in diverse ecological settings in western Kenya. Med Vet Entomol

Abstract

The microbial larvicidesBacillus thuringiensisvar.israelensis(Bti) andBacillus sphaericus(Bs) (Bacillales: Bacillaceae) are well known for their efficacy andsafety in mosquito control. In order to assess their potential value in future mosquitocontrol strategies in western Kenya, the current study tested the susceptibility of fivepopulations ofAnopheles gambiaecomplex mosquitoes (Diptera: Culicidae), collectedfrom five diverse ecological sites in this area, toBtiandBsunder laboratory conditions.In each population, bioassays were conducted with eight concentrations of larvicide(Bti/Bs) in four replicates and were repeated on three separate days. Larval mortalitywas recorded at 24 h or 48 h after the application of larvicide and subjected to probitanalysis. A total of 2400An. gambiaecomplex larvae from each population weretested for their susceptibility toBtiandBs. The mean (±standard error of the mean,SEM) lethal concentration values ofBtirequired to achieve 50% and 95% larvalmortality (LC50and LC95) across the five populations were 0.062 (±0.005) mg/Land 0.797 (±0.087) mg/L, respectively. Corresponding mean (±SEM) values forBswere 0.058 (±0.005) mg/L and 0.451 (±0.053) mg/L, respectively. Statistical analysisindicated that the five populations ofAn. gambiaecomplex mosquitoes tested were fullysusceptible toBtiandBs, and there was no significant variation in susceptibility amongthe tested populations