Increasing needs for innovative control tools against the dengue vector Aedes aegypti have prompted investigations into the development of specific mycoinsecticides. The entomopathogenic fungus Metarhizium anisopliae attacks both larval and adult stages, but its ovicidal activity against A. aegypti is still little explored. This study reports important findings about the effectiveness of conidia formulated in water and oil-in-water emulsions and of direct and indirect application techniques against A. aegypti eggs. The ovicidal activity of M. anisopliae increased with higher conidial concentrations regardless of the application technique, and larvae elimination concentrations were lowest with oil-in-water-formulated conidia (LEC50 ≤ 4·8 × 103 conidia cm−2 and LEC90 ≤ 1·9 × 105 conidia cm−2, respectively). Conidia eventually stimulated larval eclosion. Consequently, the indirect application of oil-based fungal formulations onto substrates where oviposition will later occur appears to be a more efficient means to infect those eggs than the direct fungal application to previously deposited eggs.Significance and Impact of the Study
The entomopathogenic fungus Metarhizium anisopliae has been extensively studied as a potential agent for biological mosquito control. This study demonstrates the potential of M. anisopliae s.l. strain IP 46, which can infect adults, larvae and eggs of Aedes aegypti, against the eggs of this important vector species by indirect applications of oil-based conidial formulations.