Evaluation of a granular formulation containing Metarhizium brunneum F52 (Hypocreales: Clavicipitaceae) microsclerotia in controlling eggs of Aedes aegypti (Diptera: Culicidae)

Authors: Weiler, Lina; Behle, Robert; Johnson, Eric; Strickman, Daniel; Rooney, Alejandro - Alex

Submitted to: Biocontrol Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/26/2018
Publication Date: 10/11/2018
Citation: Weiler, L., Behle, R.W., Johnson, E.T., Strickman, D.A., Rooney, A.P. 2018. Evaluation of a granular formulation containing Metarhizium brunneum F52 (Hypocreales: Clavicipitaceae) microsclerotia in controlling eggs of Aedes aegypti (Diptera: Culicidae). Biocontrol Science and Technology. 29:68-82. https://doi.org/10.1080/09583157.2018.1530342.
DOI: https://doi.org/10.1080/09583157.2018.1530342

Interpretive Summary: Control of container-breeding mosquitoes targeting larvae and adults heavily relies on insecticide treatments that are potentially hazardous to humans and the environment. The purpose of this study was to explore the feasibility of an ovicidal control strategy targeting the eggs of Aedes aegypti, the yellow fever mosquito, by utilizing the beneficial fungus Metarhizium brunneum. We chose to target eggs because a successful treatment that kills larvae before they hatch would substantially reduce mosquito populations more than convential treatments that target hatched larvae or adults. We found that the fungus M. brunneum is able to infect larvae while they are still in the egg, which resulted in a considerably high mortality rate in the laboratory sample. These results demonstrate the feasibility of using M. brunneum as an ovicidal biocontrol agent for container-breeding mosquitoes.

Technical Abstract: Successful use of microbial biological control agents such as fungal entomopathogens to kill egg-encased larvae would provide an effective strategy for controlling mosquito populations, as it would allow for a greater proportion of the population to be controlled before it was able to disperse away from oviposition sites. The purpose of this study was to evaluate the ovicidal activity of Metarhizium brunneum F52 (Mb F52) for targeting eggs of the yellow fever mosquito, Aedes aegypti. Premature eclosion of eggs was observed starting at 2-3 days subsequent to Mb F52 exposure, and up to 88% of the treated eggs eclosed prematurely within 10-14 days post-treatment. Survival of larvae from treated eggs was significantly less when compared with untreated eggs at 7, 10, and 14 days post-treatment. Only 27% of treated eggs produced viable larvae after 7 days, and 7% and 8% produced larvae after 10 and 14 days, respectively. Treating eggs with increasing concentrations of conidia resulted in an increased incidence of premature eclosion at 7 days post-treatment. Further analysis revealed that protease activity was a contributing factor to premature eclosion. Although it is not clear at this time if the proteases involved were from the fungus or the mosquito, it is evident that infection with Mb F52 induces protease activity in the infected egg regardless of its origin. Our results demonstrate that Mb F52 is a promising candidate for control of A. aegypti and that fermentative production of Mb F52 microsclerotia as the active propagule has potential for use as a mosquito ovicide.