Abstract:The spiraling whitefly, Aleurodicus dispersus Russell, is an invasive pest, which presents tremendous risk to fruit tree, vegetable and ornamental plant products in China. The egg and young nymph of the spiraling whitefly are small in size, have high degree of morphological similarity with other whitefly species and can be carried and spread easily. It is difficult to discriminate this whitefly species from others by morphological identification. In our study, a method was described for the development of DNA marker for diagnosis the spiraling whitefly based on sequence characterized amplified region (SCAR). A DNA fragment of A.dispersus, which absent in other closely related whitefly species, was identified by RAPD-PCR analysis. After cloning and sequencing the target fragment (632bp, GenBank accession no.: HM240855), one pair of SCAR primers was developed, which could amplify a single fragment of 307bp in length. Specificity tests performed with this pair of primers showed all A.dispersus specimens were detected, and no cross reactions with other whitefly species were observed. The method was tested and proved to be applicable for single egg, first to third stage instars, red-eyed-nymph, male and female adults of A.dispersus. Moreover, the 307bp DNA fragment could be clearly identified when the dilution was 1/6400 of an A.dispersus female adult for all replicates. This method will make it possible for on-site diagnostic testing, routine screening of seedlings of flowers, ornamentals and forests at ports of entry, facilitate monitoring of spread, prevention of new incursions, and further damage caused by A.dispersus in China.