Fariba Sohrabi

This research was conducted to evaluate the compatibility of the entomopathogenic fungus, Beauveria bassiana with some plant essential oils (EOs) against the red flour beetle, Tribolium castaneum under laboratory conditions. Three isolates of B. bassiana, including IRAN1395C, OZ1 and OZ2, were assayed against the adult insects by the method of wheat diet incorporation. Mortality caused by fungi at a concentration of 108 conidia ml−1 ranged from 68.3 to 73.3%. Also, fumigant toxicity of EOs from pennyroyal (Mentha pulegium), rosemary (Rosmarinus officinalis) and peppermint (Mentha piperita) was evaluated on adult insects. All EOs were effective against T. castaneum, and among them, pennyroyal EO with the lowest LC50 value (7.33 μl/l air) was the most toxic compound. Effects of the sublethal concentration (LC10) of plant EOs on mycelial growth and sporulation of the fungi were evaluated and found that all EOs were compatible with B. bassiana isolates, except peppermint and rosemary EOs, which were toxic to OZ1 isolate. Investigating the effects of the integrated application of plant EOs and fungi showed that sublethal LC10 concentrations of pennyroyal, rosemary, and peppermint EOs, increased the sensitivity of T. castaneum adults to B. bassiana infection (additive effect), except for the combination of peppermint and rosemary EOs with OZ1 isolate, where antagonistic interaction was observed. Our results suggest that isolates of B. bassiana have the potential to combine with the tested plant EOs for the integrated control of T. castaneum in stored products.