Nationwide occurrence of Bemisia tabaci Q biotype was identified from 2005 May to 2007 Dec. in total 28 cities/counties of 9 provinces such as Goyang (Kyung-gi), Gangnung (Gang-won), Jincheon (Chung-buk), Buyeo (Chung-nam), Seongju (Kyung-buk), Geoje (Kyung-nam), Bukjeju (Jeju). Host plants of the scale of B. tabaci Q biotype were over 15 crops of tomato, sweet pepper, hot pepper, eggplant, etc. and total 12 species of weeds such as Veronica persica, Ipomoea lacunosa, Conyza sumatrensis, I. hederacea, Xanthium canadense, Humulus japonicus, Boehmeria nivea, Artemisia vulgaris, Paederia scandens, Acalypha austeralis, Brassica juncea, Rumex crispus. For molecular identifying Bemisia tabaci B and Q biotypes, and Trialeurodes vaporariorum, for which it is difficult to distinguish morphologically, sequences of mitochondrial 16S rDNA and CO I (Cytochromoxidase I) gene were analyzed and restriction enzymes were selected for biotypespecific cleaved bands. As the results, Hinf I for 16S rDNA and Vsp I for CO I gene made specific band patterns for the B and Q biotypes in gel electrophoresis. Thus these methods were able to identify those biotypes and species without DNA sequence analysis. Populations of the Q biotype were collected in each regions of Korea from 2005 to 2007, and they were genetically compared using CO I gene sequences. Thus the populations were divided by three different groups which were introduced over 3-4 times before 2007 from different population sources. Geoje and Jeju were suggested as the first regions of introduction. Especially the populations in the first introduced regions were highly homologous with the Q biotype of Japan. In addition, infection pattern of secondary symbionts in populations of the B and Q biotypes in Korea were different from the Israeli populations. Thus it is suggested that Japan is the main source of B. tabaci Q biotype introduced to Korea. In addition, populations of the both of B and Q biotype in Korea were infected by Haemiltonella, which is more effectively related to the transmission of tomato yellow leaf curl begomovirus (TYLCV). Therefore it is needed to monitor continuously if the outbreak of begomovirus vectored by B. tabaci. In this molecular phylogenetic analysis, it was shown that the population of B. tabaci Q biotype in weed plants near greenhouse was introduced to crop plants in greenhouse. Therefore we understand that weed control is important to inhibit recurrence of B. tabaci in greenhouse. Three species of begomovirus, sweet potato leaf curl virus (SPLCV), tobacco leaf curl virus (TLCV), and TYLCV, were reported after introduction of B. tabaci in Korea. Especially Korean government removed all plants in the first TYLCV-occurred greenhouse in 2008. Multiplex PCR diagnosis between TLCV and TYLCV was developed for the more rapid and accurate monitoring. TLCV and TYLCV strains occurred in Korea were highly homologous with strains of Japan. Therefore these results support our suggestion that Japan is the main source of B. tabaci Q biotype introduced to Korea.