The cosmopolitan silverleaf whitefly, Bemisia tabaci which had coexisted with Trialeurodes vaporariorum in Northern China for many years, has become the dominant species in the last years. Recent reports show that it is gradually displacing the other greenhouse whitefly species. Neonicotinoid, which includes nitenpyram, is a major group of insecticides used against whiteflies in various crops. When exposed to low doses of insecticides, insects may develop resistance by adapting physiologically. The short- and long-term effects of nitenpyram on insecticide sensitivity in B. tabaci biotype B and T. vaporariorum adult populations have been compared in the present study. After being exposed to LC25 of nitenpyram for 24 h, the B. tabaci biotype B adults showed no significant change in susceptibility to nitenpyram or to five other insecticides: imidacloprid, acetamiprid, abamectin, chlorpyrifos and beta-cypermethrin. By contrast, exposure to the LC25 of nitenpyram for 24 h led to a significant increase in the susceptibility of T. vaporariorum to nitenpyram and imidacloprid, by 1.8- and 2-fold, respectively. When exposed for seven generations to the LC25 of nitenpyram, B. tabaci developed 6-fold resistance to nitenpyram, and 3.1- and 5-fold cross-resistance to imidacloprid and acetamiprid, respectively, whereas T. vaporariorum developed lower resistance (3.7-fold) to the nitenpyram and very low cross-resistance to imidacloprid (2.5-fold). The higher adaptable nature of B. tabaci (demonstrated here in the case of nitenpyram) when exposed to low doses of insecticides may provide a selective advantage when competing with T. vaporariorum in crops.