Adult individuals of B. tabaci and other whiteflies were collected from various host plants, such as tomato, pepper, ridge gourd, bean , okra, eggplant, and guava, grown in Bangladesh, Myan mar, Nepal, China, the Philippines, and Korea. In Bangladesh , we collected bean, okra, and eggplant from the southern and northern parts of the country during 2010-2011 , immediately preserved samples in 99% ethanol , and stored them at -20°C for further analysis. Adults of B. tabaci B and Q biotypes were collected from cucumber, sweet melon , and tomato plants grown throughout Korea in 2010 in order to compare the morphologies and genetic sequences of foreign whiteflies.Biotype of B. tabaci was determined by amplification of mitochondrial COi gene fragments from extracted genomic DNA samples. The presence of Arsenophonus in whiteflies was determined using specific primer sets for Arsenophonus by amplification of 23S rDNA gene fragments. The occurrence of TYLCV on cultivars of various horticultural crops was surveyed in different regions . TYLCV acquisition by B. tabaci was determined using a TYLCV-specific primer set that can amplify conserved intergenic sequences. PCR reactions were performed in a 20 mlmixture containing 5x SuperTaq PCR buffer (10 mM Tris-HCL, 40 mM KCI , l.5 mM MgC12 , pH 9.0), 2.5 mM dNTPs, 0.5 M of each primer , 1 u nit of SuperTaq DNA pol ymerase (SuperBio Co, Korea), and 1 mg of DNA as a tem plate. The mixtures were amplified using a PTC-200 thermal cycler (MJ Research , Watertown, MA, USA) wi th 5 min of initial denaturation at 95°C, 35 cycles of annealing (30 sec at 95°C, 30 sec at 60°C, 45 sec at 72°C), and 10 min of extension at 72°C. The PCR products were visualized on a 1 .0% agarose gel containing ethidium bromide. Expected PCR products were excised from the gel and purified using the Wizard PCR preps DNA purification system (Promega, Madison, WI, USA) and sequenced either directly or by cloning into pGEM-T easy plasmid vector.Sequences of the PCR products were determined using a Big Dye Terminator Cycle Sequencing Kit (Appl ied Biosystems, Foster City, USA) and analyzed using a 3730XL DNA Sequencer (Applied Biosystems , Foster City , USA). Databases were searched using the BLAST algorithm in NCBI, and sequences were aligned using the MUSCLE program. The 23S ribosomal DNA sequences of Arsenophonus were analyzed using Bayesian Mr Bayes 3.0 software. Four Metropolises-cou pled Markov Chain Monte Carlo (MCMC) chains were run until standard divergence of the split frequencies become lower than 0.0 l. A ll sequences were analyzed over 10 million generations, and four sequences were sampled every 100 generations. The first 25 % of burn-in (SUMP and SUMT) cycles were discarded prior to the construction of consensus tree, which were visualized by MEGA 4 0.