Efficacy and horizontal transmission of Beauveria bassiana and its synergistic activity with diflubenzuron against the house fly, Musca domestica L.

ABSTRACT

Resistance of house flies to chemical insecticides is increasing in the world, thus calling for sustainable control methods of flies. In this study, larvicidal and adulticidal activities of Beauveria bassiana strain DEBI 008 against the house fly were evaluated. Also, we examined the horizontal transmission of the B. bassiana between adult house flies of both sexes. Then, the susceptibility level of immature house flies to diflubenzuron was determined. In addition to synergistic effects, we investigated the combining low doses of B. bassiana and diflubenzuron on the house fly larvae. In the pathogenicity assay using direct application, the mean lethal concentration values (LC₅₀) were estimated for larvae (4.71×10⁶, conidia/ml) and adults (5.65×10⁷, conidia/ml) after 10 days. Based on mean lethal time (LT₅₀) of adult house flies, it was observed that LT₅₀ at the high concentration of 1 × 10⁸ conidia was in the range of 4.89 days with 100% mortality; LT₅₀ at the lowest concentration of 10⁵ conidia ranged from 10 to 15 days with 48% mortality. The results of B. bassiana in horizontal transmission assays on adults also showed that LT₅₀ for the females infected by horizontal transmission was 5.33 days with 100% mortality; meanwhile, for males horizontally infected with 100% mortality, this was 6.11 days. The susceptibility of the house fly population to diflubenzuron (LC₅₀) was 1.21 (mg/ kg), and high mortality was recorded at the highest concentration treated (6 mg/ kg) with 89.33% mortality. Synergistic interactions between B. bassiana and diflubenzuron were observed with the increased mortality rates of the combined treatment. The most significant synergy based on Finney’s method was the combination of LC₂₅ (B. bassiana)+ LC₂₀ (diflubenzuron) (χ²  = 60.75). Therefore, combined use in a synergistic manner could result in the enhanced biological control by accelerating the B. bassiana strain and diflubenzuron. The results of this study could be, therefore, helpful for integrated pest management to control the house fly.

KEYWORDS:

• Entomopathogenic fungi
• synergistic effects
• insect growth regulator
• Musca domestica L
• integrated pest management

Acknowledgments

The authors are grateful to the Research Council of Isfahan University of Technology for supporting this work.

Disclosure statement

No potential conflict of interest was reported by the author(s).