Effectiveness of Metarhizium anisopliae formulations against dengue vectors under laboratory and field conditions

ABSTRACT

The oviposition behaviour of Aedes aegypti and the effectiveness of Metarhizium anisopliae conidia formulated in water or oil-in-water against A. aegypti adults and eggs were tested in multi-choice and no-choice tests in oviposition devices under laboratory conditions. Both females and males rested in the devices, regardless of the formulation, and were not repelled by the presence of conidia (up to 10⁶ conidia/cm²) without oil or formulated with oil on treated filter paper arranged in the device. However, at higher oil concentrations (≥0.1 μl/cm²), regardless of the presence of conidia, the number of eggs laid by gravid females on the filter paper dropped. The susceptibility of adults, especially of males, to fungal infection increased up to a 15-day incubation. An elevated number of larvae (≥41%) eclosed from eggs laid on the moistened filter paper in the device even without submersion of eggs in water, and these larvae subsequently died. In the laboratory, 1 μl/cm² oil combined with 10⁶ conidia/cm² clearly reduced eclosion to 1.8% after submersion of eggs in water compared to ≥13% eclosion in the control. In field tests in Goiânia, Brazil, eclosion of aedine larvae from eggs laid on filter paper previously treated with oil-in-water formulated conidia dropped to between 0% and 36% compared to 22–50% in the control. Promising results of laboratory and field tests with M. anisopliae formulated in water or oil-in-water and tested in a device emphasised the effectiveness of a fungus-based formulation for aedine mosquitoes in peridomestic areas.

KEYWORDS:

• Biological control
• entomopathogenic fungi
• mosquitoes
• vectors
• dengue transmission

Acknowledgements

The authors thank Welington T. Rocha (SMS-GO) facilitating the field studies, and Richard A. Humber (USDA-ARS, Ithaca, NY) for the critical review of the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by a grant awarded by the Coordination for the Improvement of Higher Education Personnel (CAPES, Brazil) to LSL.