LARVICIDAL ACTIVITY OF BACILLUS THURINGIENSIS, B. SUBTILIS AND B. CEREUS AGAINST AEDES, ANOPHELES AND CULEX MOSQUITO LARVAE

Mosquito vectors transmit some of the world’s most serious vector-borne diseases such as malaria, encephalitis, filariasis, yellow fever, dengue fever and Chikungunya fever among others. Therefore, strategies aimed at controlling mosquitoes are of a major public health interest. Bio-insecticides continue to attract interest because they are environmentally friendly alternatives to synthetic pesticides, with limited or no toxicity to non-target animals and humans. In a completely randomized experimental design, the larvicidal activity and diagnostic concentration of cell free culture supernatants (CFCS) of three Bacilli species (B. thuringiensis, B. subtilis and B. cereus) against the larvae of three mosquito genera (Aedes, Anopheles and Culex) at six concentration levels (0%, 10%, 20%, 30%, 40% and 50%) were determined and their mortality rates observed over a 72-hour period. Bacillus cereus at 30% and 40% concentrations were very effective on all the three mosquito genera. Aedes (100%) and Anopheles (96%) larvae were sensitive to all concentrations of B. subtilis but not Culex (56%). Bacillus thuringiensis had higher larvicidal activity on Culex and Aedes larvae as compared to Anopheles. B. cereus and B. subtilis CFCS had better larvicidal activities against Aedes, Culex and Anopheles mosquito larvae as compared to B. thuringiensis. Despite the three mosquito larvae recorded mortality after two hours post exposure to the three bacilli supernatants at various concentrations, only the mean mortalities recorded by the 50% and 40% treatment on the Anopheles larvae were statistically significant with sig. values of P = 0.024 and P = 0.018 respectively. The present study proved that the larvicidal properties of the Bacillus species can be adopted for large-scale vector control following further investigations.