Mosquitocidal Bacillus thuringiensis from Nigerian soils

Abstract

Out of 85 Bacillus thuringiensis strains isolated from Nigerian soils, 18 were larvicidal to Aedes aegypti, Culex quinquefasciatus and Anopheles gambiae . At 10 −6 dilution of the final whole culture (FWC), the 11 most active strains, code-named GSC1, GSC3, GNA13, GNA14, OGL8, BUS4, BUS5, OBG1, OBG4, OBG8 and BAR3 produced mortality of 11.7–61.7% and 3.3–48.3% in Ae. aegypti and in C. quinquefasciatus fourth instars respectively. At 0.5 × 10 −5 dilution of the FWC, the B.t . strains caused mortality in An. gambiae larvae ranging from 31.7 to 94.1%. All the 18 mosquitocidal isolates belonged to the subspecies israelensis , i.e. serotype 14. Microscopic examination revealed all the isolates to be typically Bacillus , with irregular or amorphous crystals of varying sizes.