Exploiting the combination of entomopathogenic fungi and Illicium verum essential oil against Aedes aegypti larvae

Here, the effectiveness of Beauveria bassiana LCM S19 and Metarhizium anisopliae LCM S01, combined with Illicium verum essential oil (EO) against Aedes aegypti larvae was investigated. The EO compounds were first identified through gas chromatography, with the primary compound being (E)-anethole. Subsequently, in silico analysis was employed to predict the biological activity of (E)-anethole, revealing 89 molecular targets, which included insecticidal activity. Next the impact of EO on fungal viability and colony growth was examined and the EO had no effect on fungal development. Next, we investigated the influence of EO on fungal viability and colony growth, revealing that the EO had no discernible impact on fungal development. Following this, individual assessments were carried out to determine larval susceptibility to EO at concentrations of 40, 60, 80, and 100 ppm, as well as with both fungal isolates at conidial concentrations of 1 × 10⁶, 1 × 10⁷, and 1 × 10⁸ conidia/mL. Larval survival was then monitored over a period of seven days. To further optimize the larvicidal potential, EO at a concentration of 40 ppm was combined with both isolates at a conidial concentration of 1 × 10⁶ conidia/mL and tested against mosquito larvae, as described earlier. The combination of M. anisopliae and EO resulted in a substantial decrease, with only 20 % of larvae surviving over a seven-day period, in contrast to approximately 50 % survival observed in the pure M. anisopliae or EO treatments. B. bassiana, whether used alone or in combination with EO, exhibited a 50 % reduction in larval survival. The combination of M. anisopliae and EO exhibited a synergistic effect in targeting Ae. aegypti larvae, whereas B. bassiana, in conjunction with EO, had an additive effect. Notably, the combination achieved its impact in just 3 days, whereas the pure fungus required 7 days to yield similar results. These findings underscore the substantial potential of combining I. verum essential oil with both fungal isolates against Ae. aegypti larvae.