COMPATIBILITY OF BEAUVERIA BASSIANA ISOLATES WITH FOUR ESSENTIAL OILS IN VITRO CONDITIONS

Beauveria bassiana and essential oils (EOs) are among the most widely studied in insect control and plant pathogenic fungi and bacteria. However, the compatibility of B. bassiana and EOs when used together is unknown. The vapor-phase technique was used to assess the compatibility of four EOs (peppermint, black cumin, chamomile, and fennel) with Turkey indigenous isolates of B. bassiana including ET10 and Bb18 under in vitro conditions. Petri plates inoculated with different concentrations (0.5, 1, 2, and 4 μL/petri) of EOs were added to the filter papers and placed on the inner surface of the Petri plates’ lid. A 5 mm mycelial plug of B. bassiana was inoculated at the center of the Petri plate and incubated for 7 days at 25 ±1 ̊C. Petri plates filled with sterile distilled water were used as controls. The experiment was conducted in a randomized plot design with three replications. Mycelial growth decreased and inhibition percentage increased in both B. bassiana isolates due to the increase in EO concentration. A low concentration of chamomile oil showed weak toxicity against both B. bassiana isolates and received an inhibition class value of 1. Peppermint oil exhibited a higher fumigation effect than other EOs against Beauveria isolates and received an inhibition class value of 4. A low concentration of chamomile oil combined with B. bassiana can be used as a potential bioagent against insect pests. Further laboratory and field trials are needed to examine the effects of EOs and B. bassiana on pests, beneficial insects, the environment, and plants