The sweetpotato whitefly, Bemisia tabaci (Gennadius), is a sap-sucking insect that harbors the essential primary symbiotic bacterium Portiera aleyrodidarum, as well as several secondary symbionts whose function is unknown. B. tabaci is considered as a species complex composed of more than 20 biotypes which are morphologically identical but may differ markedly from each other both genetically and biologically. All Israeli B. tabaci tested to date belong to either the B or the Q biotypes. In this work the correlation between secondary symbionts composition to the whitefly's biotype and host plant was studied. 18 field populations were collected from various host plants and geographic regions in Israel during the fall of 2005. Secondary symbionts' identity and the host's biotype were determined using PCR with specific primers. The secondary symbiont Hamiltonella was detected only in the B biotype whiteflies (100% infection) whereas Wolbachia and Arsenophonus were detected only in Q biotype individuals (33% and 87% infection respectively). 45%-100% of both biotypes harbored Rickettsia. Secondary symbionts incidence did not differ among host plants. The localization of Hamiltonella and Arsenophonus in B. tabaci was studied using Fluorescence in-situ Hybridization. Both symbionts were found to be localized inside the bacteriocytes, confined with Portiera during all developmental stages, as opposed to the previously reported Rickettsia distribution in the haemolymph. The association found between whitefly biotypes and secondary symbionts suggests a possible contribution of these bacteria to host characteristics such as insecticide resistance, host range, virus transmission and speciation.