Biocontrol potential of Bacillus thuringiensis isolated from soil samples against mosquito larvae

Abstract

A major challenge for achieving successful mosquito control is overcoming insecticide resistance. The potential of Bacillus thuringiensis isolated from different soil samples as a control strategy of mosquitoes and monitoring of larvae susceptibility was investigated in this research. Larvicidal activity of Bacillus thuringiensis on mosquito larvae was assessed by isolating them from different soil habitats at Okitipupa. The isolated organisms were confirmed as Bacillus thuringiensis based on biochemical characterization and microscopic observation. Two out of the six isolates of Bacillus thuringiensis obtained from the soil samples labeled 6ORD1 and 4OD3 were used for the purpose of this study. The larvicidal activities (which were measured by mortality rate and change in morphology of the larvae) were observed at 10^-1, 10^-2, 10^-3, 10^-4, and 10^-5 dilution factors and at intervals of 4, 12 and 24 hours on the mosquito larvae. The isolates of Bacillus thuringiensis showed a slight level of variation in their larvicidal activity. Both isolates 40D3 and 60D1 caused 100% mortality of the larvae at the highest concentration of 10^-1 at 4 hours while 100% mortality was recorded in other dilution factors at 12 hours. In both control system (distilled water and rain water) 100% mortality was recorded at 24 hours. From this study, it is concluded that Bacillus thuringiensis is a very potent biolarvicide that brings about mortality of mosquito larvae at a short duration of time.

Keywords: Malaria, Mortality, Larvicidal, B. thuringiensis, Insecticides