Susceptibility of three Colombian Aedes aegypti Linnaeus (Diptera: Culicidae) populations to a Lysinibacillus sphaericus formulation

The increased incidence of vector-borne diseases and insecticide resistance in mosquitos constitute public health concerns in the tropics. Biological control is an effective alternative in the management of Aedes aegypti Linnaeus populations. Lysinibacillus sphaericus a bacterium proved to be harmless for non-target organisms has shown promising entomopathogenic activity. In Colombia, the control of A. aegypti using L. sphaericus has not been contemplated as part of vector control programmes. To assess the susceptibility of three A. aegypti populations to a L. sphaericus formulation consisting of vegetative cells of 2362 and III(3)7 strains, simulated-field bioassays were conducted in the municipalities of Ricaurte in Cundinamarca and Tauramena in Casanare, as well as in the municipal inspection of San Joaquin, Cundinamarca. Sixty larvae were deposited in a test device, which contained nine litres of chlorine-free tap water and 100 ml of the bacterial formulation (10(9) CFU/ml). Six replicates were set-up for treatment with bacteria and for the control. Larvae mortality was recorded at 24 and 48 hr. The three A. aegypti populations were susceptible to L. sphaericus formulation with a mortality rate higher than 90% at 48 hr. The formulation of L. sphaericus comprised of vegetative cells of 2362 and III(3)7 strains showed promising results that could guarantee the implementation of this formulation to control of A. aegypti populations.