Virulence of entomopathogenic fungi against Culex pipiens: Impact on biomolecules availability and life table parameters

Culex pipiens mosquitoes considered as vectors for many arboviruses such as the West Nile virus and encephalitis virus showing a global impact on human health. The natural management of the aquatic stages of this pest is crucial for maintaining an insecticide-free and sustained environment. The present work focused on studying the biological and biochemical effects of the entomopathogenic fungi: Metarhizium anisopliae, Beauveria bassiana, and Paecilomyces lilicanus, against 3(rd) instar larvae of Culex pipiens laboratory colony. The results revealed that M. anisopliae showed maximum larval mortality (88%) with the lowest lethal time (LT(50)) (22.6 hrs) at 10(8) spores/ml followed by B. bassiana (73.33%) with LT(50) (38.35 hrs), while P. lilicanus showed minimum percent mortality (65%) with highest LT(50) (51.5 hrs). The median lethal concentration (LC(50)) values were found to be 1.027 × 10(5) spores/ml for M. anisopliae, 1.24 × 10(6) spores/ml for B. bassiana, while it was 8.453 × 10(6) spores/ml for P. lilicanus. A reduction in female fecundity, number of hatched eggs, pupation and adult emergence percentage were recorded. The biochemical analysis of the treated larvae revealed different quantitative decrease in total soluble proteins, lipids, and carbohydrate hydrolyzing enzymes compared to control. Histopathological effects of fungal infection upon insect cuticles, muscles, and midgut were investigated. Based on the obtained results, M. anisopliae proved its superior virulent effect as a bio-control agent against Cx. pipiens.