Evaluation of the Larvicidal Activities of <i>Bacillus Sphaericus</i> on <i>Culex</i> Mosquito Found in Sokoto

Abstract

Studies on the larvicidal activities of Bacillus sphaericus, against Culex quinquefasciatus mosquitoes found in this area (Sokoto), was carried out. The B. sphaericus (SPH 88) was obtained from Paseur Institute in Paris (France) in the form of a water dispersible powder. About 50mg of the powder was dissolved in 10ml sterile distilled water. From this stock, 1:100 dilution was made. Subsequent volumes of 15, 30, 60, 90, 100 and 120µg/l were fetched using micropipettes and added to beakers containing 150ml sterile distilled water. The mosquito larvae added to these beakers were obtained from reared mosquitoes in the laboratory. Twenty-five 4th instar larvae were placed in each beaker and left for 24 hours for larval mortality at room temperature. The larvicidal activities determined showed that Culex quinquefasciatus mosquito from this part of the country is highly sensitive to this bacterium. Lethal concentrations (LC₅₀) in µg/l determined from a plot of percentage mortalities against concentrations was 0.004µg/l while LC₉₀ was 0.019µg/l indicating the B. sphaericus attacks the Culex mosquito with a consequent killing of over 90% of the population under test. Statistical analysis conducted using analysis of variance indicated that there was no significant difference in the overall larvicidal activities at 5% confidence limit (F>0.05).



Keywords: Bacillus, Sphaericus, mosquitos, Sokoto


Bio-Research Vol.1(1) 2003: 29-34