Larvicidal Activity and Influence of Bacillus thuringiensis Var. Israelensis on Aedes albopictus Oviposition in Ovitraps During A Two-Week Check Interval Protocol

Abstract

Toxicity persistence of Bacillus thuringiensis var. israelensis (Bti) was evaluated in laboratory and field trials to develop a new protocol for Aedes albopictus monitoring. In the laboratory, the residual toxicity of 5 Bti formulations was compared using the percentage mortality at days 4, 8, 12, and 16 of Culex pipiens larvae exposed for 24 h to Bti treatments. The results showed a good performance of all tested formulations (>97% mortality at day 14, for all the formulations), but only Vectobac 12AS at the concentration of 1 ml/liter showed an efficacy of 100% for 2 wk. A field study was designed to test the effect of Bti on the ovitrap check interval or influence of ovipositional response of gravid Ae. albopictus females. Three different ovitrap treatments were used: ovitraps with tap water checked weekly; ovitraps with tap water checked every 2 wk; ovitraps with Bti (Vectobac 12AS, dose of 1 ml/liter) checked every 2 wk. Our study demonstrated that in the ovitrap, the toxic action of a 1% solution of Bti was maintained for at least 14 days with mortality of 100% and that rainfall did not seem to negatively influence the residual action of Bti. Therefore the probability that the larvae may complete the developmental cycle in ovitraps with Bti seems to be very low. The oviposition activity index showed that Bti enhances the oviposition rate of Ae. albopictus by 17.4%.

Aedes albopictus (Diptera: Culicidae) Population Size Survey in the 2007 Chikungunya Outbreak Area in Italy. I. Characterization of Breeding Sites and Evaluation of Sampling Methodologies

“…According to our Þndings, which are in agreement with Allan and Kline (1998) and Carrieri et al (2009), in Ae. albopictus the females per egg rate did not seem to be inßuenced by the egg density.…”

Monitoring temporal fluctuations of Culex quinquefasciatus using oviposition traps containing attractant and larvicide in an urban environment in Recife, Brazil

“…This reinforces the use of Bti as an efficient larvicide against urban mosquito species from the Culex and Aedes genera. In addition to the long persistence of Bti larvicidal activity in shaded areas , and the fact that no mosquito resistance has been recorded after decades of Bti use (Becker 1997, Regis et al 2001, this larvicide can help attract gravid females (Santos et al 2003, Stoops 2005, Carrieri et al 2009, Barbosa et al 2010, potentially promoting the concentration of mosquito eggs in lethal ovitraps. Due to the safety guaranteed by the persistent larvicidal action of Bti, frequent inspections of the traps, as performed throughout this study, is unnecessary.…”

“…israelensis (Bti) and Bacillus sphaericus may function as attractants for Aedes and Cux. quinquefasciatus mosquitoes (Poonam et al 2002, Santos et al 2003, Stoops 2005, Barbosa et al 2007, Carrieri et al 2009). …”

Laboratory and field evaluation of the effects of the neonicotinoid imidacloprid on the oviposition response of Aedes (Stegomyia) aegypti Linnaeus (Diptera: Culicidae)

“…Carrieri et al (2009) found that ovitraps containing 1% Bacillus thuringiensis var. israelensis (VectoBAC 12AS formulation) did not affect the oviposition response of gravid Aedes albopictus females and that it had a 100% lethal effect for at least 14 days, enough time to disrupt the reproductive cycle of Aedes.…”