Exposure Timing and Method Affect Beauveria bassiana (Hypocreales: Cordycipitaceae) Efficacy Against House Fly (Diptera: Muscidae) Larvae

House flies, Musca domestica L., are widely recognized for their ability to develop resistance to chemical insecticides so alternative control strategies are desired. The use of entomopathogenic fungi such as Beauveria bassiana (Balsamo) Vuillemin to manage house fly populations has shown promising results; however, the success of using this fungus against larval house flies varies widely. The overall objective of this study was to examine factors that may influence efficacy of B. bassiana treatments against larvae. When a high concentration (4 x 10(11) conidia/ml) was applied to first- and second-instar larvae in rearing medium, there was a significant reduction in pupation and adult emergence rates. Treating third-instar larvae at the same concentration did not result in a significant reduction of pupation or adult emergence. Temperature (22 versus 32 degrees C) and media composition (diets with- and without propionic acid) did not affect the B. bassiana treatment efficacy against house fly larvae. The narrow time window of vulnerability of larvae and the high doses required to infect them indicate that B. bassiana has little potential as an operational biocontrol agent for house fly larvae.

Automated summary

The study showed that high concentrations of Beauveria bassiana had a significant inhibitory effect on first- and second-instar house fly larvae, but not on third-instar larvae. However, environmental factors such as temperature and medium composition did not significantly affect the efficacy of B. bassiana against house fly larvae.