Factors Governing Mosquito Susceptibility To Bacillus Sphaericus Strains

Abstract

Three lyophilized strains of Bacillus sphaericus (1593-4, 2297 and SSII) were tested against four different mosquito species. Culex pipiens larvae demonstrated the highest level of susceptibility towards the 3 B. sphaericus strains followed by Culiseta longiareoleta, Anopheles sergentii and then Aedes caspius. Tolerance of C. pipiens larvae to infection by B. sphaericus 1593-4 increased with the increase of larval age. The larvicidal activity increased with the increase of bacterial growth age till 48 hours when it reached complete sporulation. B. sphaericus strains 1593-4 and 2297 cultured on tryptose yeast extract medium produced the highest mortality of 3rd instar larvae of Culex pipiens, followed by tryptose soy broth media, nutrient broth media and then casien hydrolysate media. Larvae treated with suspensions of bacteria at high concentrations for few hours gave similar mortality levels as when treated for 48 hours.