Biological control of Culex pipiens mosquito by local bacterial isolates

Abstract

In this work, 62 bacterial and actinobacterial isolates were isolated from different soil samples and screened for their larvicidal activities against the 3 rd instar Culex pipiens larvae. Two potent isolates that showed high mortality rate were identified by16S rRNA gene sequencing as Bacillus subtilis (MH370499) and Streptomyces griseoruber (MH370498). Optimizing the environmental and nutritional conditions increased the mortality percentage of B. subtilis from 82.9% to 100% and S. griseoruber from 69% to be 100% LC 50 and LC 90 of B. subtilis were 13.68% and 28.29%, while for S. griseoruber were 5.79% and 18.53% respectively. The best solvent for active substance from B. subtilis extraction was ethyl acetate, while for S. griseoruber was hexane. The GC-MS analysis of S. griseoruber detected the presence of antilarval compounds ambrosin and triacontane. In addition, the larvicidal surfactin produced by B. subtilis was detected by haemolysis.