Synergistic Effects of Entomopathogenic Fungi (Beauveria bassiana and Metarhizium anisoplae) Extracts against the Developmental Stages of Anopheles Mosquitoes

Abstract

The increasing resistance of Anopheles mosquitoes to conventional insecticides has intensified the search for environmentally friendly biological control agents. Entomopathogenic fungi such as Beauveria bassiana and Metarhizium anisopliae have shown considerable potential for mosquito management. This study evaluated the efficacy of B. bassiana, M. anisopliae, and their combination against the egg, larval, and pupal stages of Anopheles mosquitoes at concentrations of 50 and 100g/mL. Bioassays were conducted using 50 and 100g/mL suspensions of B. bassiana, M. anisopliae, and their combined formulation. The percentage of egg hatchability and mortality of larval and pupal stages were determined and compared across treatments. At 50g/mL, B. bassiana recorded higher ovicidal activity (60% unhatched eggs) than M. anisopliae (45%), while the combined treatment resulted in 50% unhatched eggs. At 100g/mL, the combined treatment achieved the greatest ovicidal effect, with 80% unhatched eggs, compared with B. bassiana (60%) and M. anisopliae (35%). M. anisopliae induced greater larval mortality than B. bassiana when applied individually, whereas the combined treatment was less effective. Both fungi produced high pupal mortality, particularly at 100g/mL, although their combination was less effective. The combined application exhibited the strongest synergistic effect, particularly against the egg stage. In conclusion, B. bassiana and M. anisopliae are effective biocontrol agents against immature stages of Anopheles mosquitoes, with their combination showing enhanced ovicidal activity at higher concentrations. The combined formulation at 100g/mL is recommended for integrated mosquito management, while further field studies are needed to validate its efficacy under natural environmental conditions.