Supplementing artificial diet with antimicrobial compounds increases the resistance of sterile males of Ceratitis capitata (Diptera: Tephritidae) applied as vectors of virulent fungi

ABSTRACT

Sterile males (SMs) of C. capitata have been proposed as vectors of entomopathogenic fungi (EF). However, they are also susceptible to virulent strains. This work evaluates the effects of supplementing the artificial diet with antimicrobial compounds on the larvae and adults of C. capitata tsl Vienna-8 and their resistance to virulent EF strains. Even a lower dose of methylparaben (MPB) (0.5 g kg^-1) inhibited the mycelial growth of Metarhizium anisopliae LCB255 and Beauveria bassiana LCB289. Sodium benzoate (BNZ) at 2.5 g kg^-1 reduced mycelial growth of both strains by 50%, while citric acid did not interfere with fungi development. Supplementing the larval and adult diets with MPB (2.0 g kg^-1) plus BNZ (2.5 g kg^-1) or only MPB significantly reduced the mortality of pupae and adults treated with LCB255 or LCB289. Feeding larvae and adults with diets amended with the antimicrobials significantly reduced SMs’ mortality and its mortality curve (p <0.05). SMs fed with the supplemented diet showed a significantly higher median survival time (8 days) than the control group (3–4 days) (p <0.05). As a result, there was an efficient transference of EF conidia to females during mating and mating attempts, thus increasing female mortality. The results were confirmed in a field-cage experiment when SMs were fed diets supplemented with antifungal compounds, which showed a higher median survival time.

KEYWORDS:

• Metarhizium
• beauveria
• methylparaben
• sodium benzoate
• horizontal transference
• sterile male

Acknowledgments

The authors are grateful to Mr. Herbert Targino for his technical support and significant help in the experiments.

Disclosure statement

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

Additional information

Funding

This research was funded by Pernambuco State Foundation for Science and Technology - FACEPE [Fundação de Amparo à Ciência e Tecnologia do Estado de Pernambuco] and Brazilian Agriculture Research Corporation – Embrapa [Empresa Brasileira de Pesquisa Agropecuária] MP3 23.16.00.072.00 and MP2 02.10.06.013.00.