Comparative virulence of Metarhizium anisopliae and four strains of Beauveria bassiana against house fly (Diptera: Muscidae) adults with attempted selection for faster mortality

Authors: WHITE, ROXIE - Former ARS Employee; Geden, Christopher - Chris; KAUFMAN, PHILLIP - Texas A&M University; Johnson, Dana

Submitted to: Journal of Medical Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/16/2021
Publication Date: 3/11/2021
Citation: White, R.L., Geden, C.J., Kaufman, P.E., Johnson, D.M. 2021. Comparative virulence of Metarhizium anisopliae and four strains of Beauveria bassiana against house fly (Diptera: Muscidae) adults with attempted selection for faster mortality. Journal of Medical Entomology. https://doi.org/10.1093/jme/tjab027.
DOI: https://doi.org/10.1093/jme/tjab027

Interpretive Summary: House flies are global pests of humans and animal agriculture. Although the flies can transmit diseases of people and animals, they also have diseases of their own, some of which can be manipulated to control them. These disease include infections with the entomopathogenic fungi Beauveria bassiana and Metarhizium anisopliae. Although these pathogens can be used to infect flies by making releases, their use as practical pest management tools has been limited by the long time that it takes for them to kill the fly. Two ways to increase the kill speed of microbial agents is to evaluate different available trains for their kill rates and to select for faster kill times in the laboratory. In this paper by scientists with USDA, ARS, CMAVE (Gauinesville) and Texas A & M University, 5 strains of fungi were compared in the lab. Three strains of B. bassiana had particularly high virulence for flies, including a strain that was isolated by an ARS scientist from house flies in Florida (NFH10). Ten generations of selection for faster kill times with NFH10 were not sufficient to result in a faster-killing sub-strain. A strain that is already available from commercial sources but not registered for house fly control was one of the superior strains. Results of the work could be used to support expansion of the label of a product that is already registered with EPA for several other pests.

Technical Abstract: Entomopathogenic fungi such as Beauveria bassiana (Balsamo) Vuillemin and Metarhizium anisopliae/brunneum (Metchnikoff)/Petch have shown promising results for managing the house fly, Musca domestica L. A primary challenge of using these biological control agents (BCAs) in field situations is the time required to induce high adult house fly mortality, typically 6-7 days post exposure. In this study, virulence of M. anisopliae (strain F52) and four B. bassiana strains were compared. The B. bassiana strains GHA and HF2 are used in commercial products and those were compared with two strains that were isolated from house flies on dairy farms (NFH10 and L90). Assays were conducted by exposing adult house flies to fungal treated filter paper disks for 2 h. The lethal time to 50% mortality (LT50) at the high concentration of 1 x 109 conidia ranged from 3.8 to 5.2 days for all five strains. GHA, NFH10, and L90 killed flies faster than M. anisopliae strain F52; HF23 did not differ from either the M. anisopliae or the other B. bassiana strains. Attempts with the NFH10 strain to induce faster fly mortality through selection across 10 fungal to fly passages did not result in shorter time to fly death of the selected strain compared with the unselected strain.