Abstract: Limited information is available with respect to Bemisia tabaci biotypes entering theUK and whether insecticide resistance within outbreak populations occurs. Using a PCR-basedTaqMan assay, historic B. tabaci interceptions were analysed, of which 57% were determined tobe Q-type and 26% B-type. A number of very recent interceptions were exclusively Q-type.Phylogenetic analysis indicated that plant origin is a good indicator of the source populations ofB. tabaci for some countries/regions but not for others. A recently established field strain (Qtype)was shown to be highly resistant to imidacloprid, acetamiprid and pymetrozine but notolerance to flonicamid was seen. The findings indicate that B. tabaci entering the UK are mostlyQ-types that may exhibit high levels of resistance to insecticides commonly used for their controland, because of this, IPM/biological strategies must be developed that remove overreliance on thechemical eradication of this insect.