Abstract: The development of insecticide resistance in field populations of Bemisia tabaci from different regions of Fujian Province, China were monitored with adult leaf-dipping bioassay. Compared with bioassay data of 2005, all field populations tested in 2009 still had high levels of resistance to the lambda-cyhalothrin, fenpropathrin and chlorpyrifos, low levels of resistance to methomyl, and no resistance to abamectin. However, resistance to the neonicotinoids imidacloprid and thiamethoxam had increased from moderate levels (23 folds and 25 folds, respectively) in 2005 to high levels (103 folds and 228 folds, respectively) in 2009 in Zhangzhou population, and low levels (1.5-3.3 folds and 1.7-5.5 folds,respectively) in 2005 to moderate levels (23-33 folds and 29-49 folds, respectively) in 2009 for other populations. The biotype of eight B. tabaci populations collected from different regions and hosts were determined according to the mitochondria cytochrome oxidase I (mtCO I ) sequence, and two different biotypes (B-biotype and indigenous whitefly) were detected. The samples collected from geographical regions and hosts showed a prevalence of the B-biotype, and indigenous whitefly (unknown biotype) existed only in croton of Zhangzhou. Host plants and temperature had limited effects on insecticide development in B. tabaci, while extensive and high frequent use of neonicotinoids could be the most important factors responsible for rapid development of insecticide resistance in field populations of B-biotype B. tabaci.

Key words: Bemisia tabaci, pesticide resistance monitoring, biotype, host plant, temperature