Effects of sublethal piperonyl butoxide （PB） on parasitization of Bemisia tabaci （Gennadius） （Hemiptera： Aleyrodidae） by Encarsia bimaculata Heraty et Polaszek （Hymenoptera： Aphelinidae） were evaluated both in cage and greenhouse experiments. When first, second and third instar B. tabaci nymphs were treated with PB, all but the first instar were significantly prolonged. Data indicated that sublethal PB could improve E. bimaculata parasitism rates without influencing parasitoid eclosion rates. Prolonged development increased rates of parasitism by E. bimaculata, from 17.6% to 24.7% in cages, presumably by increasing the duration of host exposure. Sublethal PB combined with E. bimaculata as an integrated approach to control B. tabaci was evaluated using life table parameters under greenhouse conditions. Indices of population trend （I） calculated from life tables were estimated at 4.6 for B. tabaci exposed to PB and parasitoids compared to 14.1 with parasitoids alone and 23.5 in un- treated controls. The results showed that after PB was sprayed and parasitoids introduced, development ofB. tabaci was delayed and the peak of each stage was postponed. The older nymphal stage had highest mortality, primarily due to mortality caused by parasitism by E. bimaculata.
