Comparative toxicity of selected larvicidal formulations against Anopheles stephensi Liston and Aedes aegypti Linn

Toxicity of selected larvicidal formulations of Bacillus sphaericus, Bacillus thuringiensis H-14 israelensis (Bti) and insect growth regulators was determined against Anopheles stephensi and Aedes aegypti, the two major urban mosquito vectors of malaria and dengue fever in India respectively. The study revealed that the formulations of Bacillus thuringiensis H-14 and IGR compounds were highly toxic against both the mosquito species but Bacillus sphaericus formulation was less toxic against Aedes aegypti and has a limited potential for use against Aedes aegypti. Of the two Bti formulations, 'Vectobac' formulation was more toxic against both the species than 'BMP-1442X' formulation. Bti formulations were more toxic against Aedes aegypti (LC50 = 0.06 and 0.14 mg/Litre) than against An. stephensi (LC50 = 0.14 and 0.81 mg/Litre), while B. sphaericus formulation was more toxic against An. stephensi LC50 = 0.031 mg/Litre than Aedes aegypti LC50 = 0.294 mg/Litre. Among different larvicidal formulations tested in this study, IGR compounds were found to be toxic against both the mosquito species at very low concentrations (EC50 values ranging between 0.0001 and 0.0004 ppm).