Laboratory evaluation of vectobac R-12AS and teflubenzuron against Culex and Aedes mosquito larvae under different physical conditions

Abstract

Vectobac R-12AS was effective in reducing larval populations of Culex quinquefasciatus, Aedes albopictus, and Aedes aegypti at the mg/L level. Susceptibility to the Bacillus thuringensis (H-14) formulation varied according to different species and strains of mosquito larvae, especially significant among albopictus strains. Teflubenzuron was also highly effective in inhibiting normal development of mosquito larvae into adults at the μg/L level. Mortality occurred mainly in the pupal stage. Lower concentrations resulted in abnormal adults partly exuviated from the pupal cases. The larvicidal property of Vectobac R-12AS was affected by temperature and larval density. Low water temperature (5°C) and high population density (200–250 larvae/L medium) favored better survival of the larvae. Similarly, the susceptibility of Bora-bora larvae to teflubenzuron increased with increasing temperatures and complete darkness. However, the pH did not cause significant change on the potency of both Vectobac R-12AS and teflubenzuron. High dosage and prolonged application of Vectobac R-12AS may impose some stress on the survival of certain small crustaceans. Likewise, a high dosage of teflubenzuron imposed a detrimental effect on the water flea, brine shrimp, and freshwater shrimp, but little or no detrimental effect on the freshwater fish investigated.