Mosquito-associated fungal communities and assessment of their entomopathogenic potential against Aedes albopictus and Culex quinquefasciatus: First report from Sri Lanka

Microbial communities play a crucial role in the survival and fitness of mosquitoes, influencing multiple stages of their life cycle. This study aimed to characterize and compare the fungal communities associated with Aedes albopictus and Culex quinquefasciatus larvae and to evaluate the entomopathogenic potential of common fungal species isolated from both genera against Aedes albopictus and Culex quinquefasciatus. Larvae (n = 240) were collected from natural and artificial breeding sites in Kandy and Galle districts. Fungi from external surfaces and total larva extract were cultured on Potato Dextrose Agar (PDA) and identified morphologically and by DNA sequencing. Four fungal species common to both mosquito genera, Aspergillus fumigatus, A. niger, Cladosporium cladosporioides, and C. langeronii, were selected for entomopathogenicity assays.  Bioassays were conducted using conidial suspensions (1 × 103^–1 × 107 conidia/mL), and mortalities were recorded at 24 and 48 hours.  Nine fungal species were isolated from Aedes larvae, with Curvularia sp. and Trichoderma sp. being the most abundant. Twenty fungal species were isolated from Culex larvae, with Cladosporium sp. predominating. Only A. niger exhibited strong larval pathogenicity against both mosquito species, with low LC₅₀ values (Ae. albopictus: 2.60 × 10⁶ and 2.17 × 10⁵ conidia/mL respectively at 24 h and 48 h; Cx. quinquefasciatus: 5.20 × 10⁵ and 4.05 × 10⁵ conidia/mL, respectively, at 24 h and at 48 h. Cladosporium cladosporioides showed the highest larvicidal activity against Cx. quinquefasciatus larvae (LC₅₀: 2.71 × 10⁵ conidia/mL; LC₉₀: 1.95 × 10⁶ conidia/mL). In contrast, Aspergillus fumigatus and C. langeronii showed relatively low larvicidal activity and were effective only against Cx. quenquifaciatus larvae. In adult bioassays, A. niger also showed notable pathogenicity against Ae. albopictus, with LC₅₀ of 7.98 × 10⁶ and 8.72 × 10⁵ conidia/mL at 24 and 48 hours, respectively. The results suggest that A. niger can be considered as an entomopathogenic fungus and could be recommended as a potential biological control agent against both larvae and adult mosquitoes.