Laboratory and semi-field evaluation of the efficacy of Bacillus thuringiensis var. israelensis (Bactivec®) and Bacillus sphaericus (Griselesf®) for control of mosquito vectors in northeastern Tanzania.

Bacterial larvicides Bacillus thuringiensis var. israelensis (Bti) and Bacillus sphaericus (Bs) have been used extensively for mosquito control. However, their efficacy varies greatly mainly due to factors related to target mosquitoes, larval habitat conditions, and inherent larvicide properties. We evaluated the efficacy of Bti (Bactivec®) and Bs (Griselesf®) for control of Anopheles gambiae complex, Culex quinquefasciatus and Aedes aegypti larvae under laboratory and semi-field conditions in northeastern Tanzania. Laboratory bioassays were conducted with five to six different concentrations of Bti and Bs, replicated four times and the experiment repeated on three different days. Larvae mortality was recorded at 24 or 48 h after the application of larvicide and subjected to Probit analysis. Laboratory bioassays were followed by semi-field trials to establish initial and residual activity of Bti and Bs. Semi-field trials were conducted in artificial larval habitats in the open sunlit ground and in "mosquito spheres". These artificial larval habitats were colonized with mosquito larvae, treated with Bti and Bs, and the impact of treatments on mosquito larvae was monitored daily. Lethal concentration values that caused 50% and 95% mortalities of test larvae (LC50 and LC95) showed that An. gambiae complex and Cx. quinquefasciatus tested were highly susceptible to Bti and Bs under laboratory conditions. Likewise, larvae of Ae. aegypti were highly susceptible to Bti, with LC95 value as low as 0.052 mg/l. However, Ae. aegypti larvae were not susceptible to Bs under practical doses of laboratory settings. In semi-field trials, all treatment dosages for Bti provided 91.0-100% larval mortality within 24 h whereas Bs resulted in 96.8-100% larval mortality within the same time-frame. Bs had a more prolonged residual activity, with pupal reductions range of 55.7-100% for 9 days at all application rates while the corresponding pupal reduction with Bti was 15.4-100% for 5 days. Due to the low residual activity of Bti and Bs tested, weekly application at a maximum label rate would be appropriate to reduce mosquito larvae in natural larval habitats. Based on laboratory findings, Bs product tested would not be recommended for use in the control of Ae. aegypti.

Derua YA ，Tungu PK ，Malima RC ，Mwingira V ，Kimambo AG ，Batengana BM ，Machafuko P ，Sambu EZ ，Mgaya YD ，Kisinza WN ... -  《-》

Wide-scale application of Bti/Bs biolarvicide in different aquatic habitat types in urban and peri-urban Malindi, Kenya.

Mwangangi JM ，Kahindi SC ，Kibe LW ，Nzovu JG ，Luethy P ，Githure JI ，Mbogo CM ... -  《-》

Evaluation of a long-lasting microbial larvicide against Culex quinquefasciatus and Aedes aegypti under laboratory and a semi-field trial.

Rique HL ，Menezes HSG ，Melo-Santos MAV ，Silva-Filha MHNL ... -  《Parasites & Vectors》

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

The microbial larvicides Bacillus thuringiensis var. israelensis (Bti) and Bacillus sphaericus (Bs) (Bacillales: Bacillaceae) are well known for their efficacy and safety in mosquito control. In order to assess their potential value in future mosquito control strategies in western Kenya, the current study tested the susceptibility of five populations of Anopheles gambiae complex mosquitoes (Diptera: Culicidae), collected from five diverse ecological sites in this area, to Bti and Bs under 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 mortality was recorded at 24 h or 48 h after the application of larvicide and subjected to probit analysis. A total of 2400 An. gambiae complex larvae from each population were tested for their susceptibility to Bti and Bs. The mean (± standard error of the mean, SEM) lethal concentration values of Bti required to achieve 50% and 95% larval mortality (LC50 and LC95 ) across the five populations were 0.062  (± 0.005) mg/L and 0.797 (± 0.087) mg/L, respectively. Corresponding mean  (± SEM) values for Bs were 0.058 (± 0.005) mg/L and 0.451 (± 0.053) mg/L, respectively. Statistical analysis indicated that the five populations of An. gambiae complex mosquitoes tested were fully susceptible to Bti and Bs, and there was no significant variation in susceptibility among the tested populations.

Derua YA ，Kahindi SC ，Mosha FW ，Kweka EJ ，Atieli HE ，Zhou G ，Lee MC ，Githeko AK ，Yan G ... -  《-》

Field testing & evaluation of the efficacy & duration of effectiveness of a biolarvicide, Bactivec(®) SC (Bacillus thuringiensis var. israelensis SH-14) in Bengaluru, India.

Uragayala S ，Kamaraju R ，Tiwari S ，Ghosh SK ，Valecha N ... -  《INDIAN JOURNAL OF MEDICAL RESEARCH》