Assessment of larvicidal activities of bacillus species isolated from soil against the mosquito aedes aegyptia (diptera: culicidae) in Sokoto, northwestern Nigeria

Abstract

Three Bacillus species (B. cereus, B. sphaericus and B. thuringiensis) known to have potentials for mosquito larvicidal properties were tested against Aedes mosquito larvae. The Bacillus species showed pronounced larvicidal activities with B. cereus having 60% mortality, B. sphaericus 84% and B. thuringiensis 56% against the mosquito tested. The lethal concentrations (LC₅₀) determined were 0.033, 0.033 and 0.029 for B. cereus, B. sphaericus and B. thuringiensis respectively. Aedes mosquitoes were more sensitive to B. thuringiensis than to other Bacillus species with determined potency of 827 ITU/mg. These results compared favourably with that of the standard B. thuringiensis from Paris, France, which recorded 100% mortality against the mosquito. There was no significant difference (P > 0.05) between the local isolates but variation exists (P < 0.05) when compared with the standard B. thuringiensis powder. Post experimental analysis using the Least Significant Difference test (LSD = 16.84) showed that the standard strain stands out different from the other three isolates. These findings strengthen the earlier reports that B. thuringiensis is a good control agent for Aedes mosquito. There is, however, the need to continue further search for Bacillus species with larvicidal potentials.

Keywords: Bacillus Species, Larvicidal Activity, Soil, Sokoto, Aedes Mosquitio.