Vol. 7, Issue 2, Part A (2020)

Author(s): Gopalan Rajagopal and Sakkanan Ilango

Abstract: Mosquito-borne diseases are major illnesses caused by pathogens and parasites in humans and animals. Some of the Bacillus toxins act as insect control agents and few are potential alternatives to chemical control because they can be innovative and more selective than chemical insecticides. On the other hand, many insects’ species may coexist in the larval development sites and are susceptible to the larvicidal activity of Bacillus toxins. Therefore, in this study, optimized native Bacillus strains from infected insects were identified by 16S rRNA gene sequencing method and to perform experiments on the larvicidal effects of the pathogenicity against third instar larvae of Culex quinquefasciatus and Aedes aegypti. The maximum larval mortality was observed after 48 hrs of exposure. The LC₅₀ for Bacillus cersus, Bacillus thuringiensis and Lysinibacillus sphaericus against the A. aegypti as 5.40×10⁸, 5.33×10⁸and 4.51×10⁸cells and for C. quinquefasciatus as 4.70×10⁸, 4.32×10⁸and 3.62×10⁸ cells in 24 hrs respectively. Findings showed that optimized native Bacillus strains have high larvicidal activity against the larvae of C. quinquefasciatus and A. aegypti whereas bacillus strains from soil sample was ineffective to the mosquitoes. The outcome of the present study identifies the improved bacterial strains B. cersus, B. thuringenesis L. sphaericus obtained from infected insects that can be used as effective and alternate larvicidal agents against the mosquito larvae of C. quinquefasciatus and A. aegypti.