Larvicidal activity of Bacillus thuringiensis subsp. israelensis (Bacillaceae) and plant extracts for the biological control of Aedes aegypti (Culicidae)

Aedes aegypti transmits viruses that cause diseases such as dengue, yellow fever, Zika and chikungunya. Chemical pesticides have been used to control this vector, but mosquitoes have developed resistance to insecticides. Biological control with microorganisms and plant extracts are effective alternatives for the management of insect vector populations and introduce less pollutants into the environment. The objective of this research was to evaluate the larvicidal activity of Bacillus thuringiensis subsp. israelensis (Bti) and extracts of Annona muricata, Ricinus communis and Sapindus saponaria for the biological control of A. aegypti larvae. For this, ethanolic extracts of seeds or fruits of the three plant species were obtained and lethal concentrations for 50 % mortality of the extracts and bacteria were determined. Subsequently, combinations of the extracts with Bti were made and the interactions were evaluated. Both bacteria and plant extracts showed larvicidal activity. Mixtures of Bti with the ethanolic extracts of R. communis and S. saponaria generated an antagonistic effect, while in combination with ethanolic extracts of A. muricata presented an independent action effect. Therefore, the addition of the ethanolic extract of A. muricata seeds to sporulated cultures of Bti could be considered more effective for the biological control of A. aegypti than with each compound separately.