Larvicidal and immunomodulatory effects of conidia and blastospores of Beauveria bassiana and Beauveria brongniartii in Aedes aegypti

Abstract

The increasing global burden of mosquito-borne diseases and the widespread development of insecticide resistance in mosquitoes have fueled renewed interest in entomopathogenic fungi as effective tools that are compatible with existing mosquito control strategies. These fungi produce different types of infective propagules, including hydrophobic conidia and yeast-like blastospores, which differ in structure, mode of infection, and virulence. In this study, we evaluated the larvicidal activity of conidial and blastospore propagules from Beauveria bassiana MBC076 and Beauveria brongniartii MBC397 against Aedes aegypti. Conidia exhibited more rapid and more potent larvicidal effects compared to blastospores, but the overall survival at seven days post-infection was similar between the two types of propagules. Interestingly, B. brongniartii blastospore infections resulted in a significantly higher proportion of pupal mortality, suggesting a delayed mode of action. Immune profiling of infected larvae indicated significant induction of antimicrobial effectors such as cecropin, defensin, and attacin, primarily in response to conidial infection. In contrast, blastospore infections were associated with reduced expression of several prophenoloxidase genes, particularly during infection with B. brongniartii blastospores. These findings indicate that different fungal species and their propagule types exert varying levels of virulence and immune modulation in mosquito larvae. This study provides insights into the infection dynamics of fungal propagules and identifies immune markers that can be leveraged to enhance the efficacy of fungal-based larvicides.