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

Abstract

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.