Whitefly, Bemisia tabaci (Gennadius, 1889) (Hemiptera: Aleyrodidae) hosting various bacteria is among the most significant insect pest causing economic losses in agricultural production. A study was conducted to determine the bacterial flora of B. tabaci and to identify the efficiency of these bacteria against B. tabaci. Samples were collected from sesame and melon plants in Mersin and Adana Provinces of Turkey in 2014. Nine bacterial strains were identified by morphological, MALDI-TOF MS and molecular identification methods to species level. Bacillus sp., Methylobacterium sp., Microbacterium sp., Serratia marcescens and Sphingomonas sp. were identified from the samples collected from sesame and Acinetobacter Iwoffii, Bacillus cereus, Staphylococcus hominis and Staphylococcus warned were identified from the samples collected from melon. To determine biological efficiency against B. tabaci adult (biotype B), whiteflies were fed with insect food as control (sucrose + water), insecticidal control (acetamiprid) and bacterial suspensions. The entomopathogenic bacteria S. marcescens isolated from B. tabaci for the first time in this study yielded an efficiency of 72% against adult whitefly. However, the other strains had efficiencies below 25%. It was concluded, given the efficiency of S. marcescens, that further research should be conducted on the pathology of entomopathogenic bacteria in pest insects.