The hazelnut leaf holer (Anoplus roboris Sufr., Coleoptera: Curculionidae) is a devastating pest of hazelnut and oak trees. It causes approximately 20-30% economic damage to hazelnut production per year in Turkey. In the present study, in order to find a more effective and safe biological control agent against A. roboris, we investigated the bacterial flora of the hazelnut leave holer, and tested them for insecticidal effects on it. According to morphological, physiological and biochemical tests, bacterial flora were identified as Bacillus circulans (Ar1), Bacillus polymyxa (Ar2), Enterobacter sp. (Ar3) and Bacillus sphaericus (Ar4) Insecticidal effects of bacterial isolates were performed on adult A. robot-is. The highest insecticidal effect determined was 61% by B. sphaericus within eight days. The insecticidal effects of the other isolates (Ar1, Ar2 and Ar3) were determined as 33%, 47% and 47% within the same period, respectively.