Abstract: In order to determine the role of Encarsia sophia in the displacement of Bemisia tabaci B biotype by Q biotype, in this study we observed the parasitizing behavior and preference of E. sophia on the Q and B biotypes of B. tabaci and investigated the effects of B. tabaci biotype on development of E. sophia in the laboratory under 27±1℃, 16L∶8D and RH 70%-80%. The results indicated that the time for outside host examination of E. sophia was not significantly different between two whitefly biotypes, whereas the time for inside host examination and oviposition on Q biotype nymph was significantly longer than that on B biotype nymph, 190.2±14.6 s vs 140.0±7.5 s. In non-choice tests, the number of Q biotype nymphs parasitized (8.1±0.5) and the total egg number (9.3±0.6) laid by E. sophia was significantly higher than those for B biotype nymphs (6.3±0.5 and 7.0±0.6, repectively), while the number of eggs loaded per nymph parasitized was not significantly different between B and Q biotypes. In choice tests, the number of nymphs parasitized (3.1±0.4), the total number of eggs laid per wasp (3.8±0.5), and the number of eggs loaded per host (1.2±0.1) for B biotype were higher than those for Q biotype (the corresponding numbers were 1.8±0.3, 1.8±0.4 and 0.7±0.1, respectively). There were no significant differences in the number of nymphs fed by E. sophia between B and Q biotypes, but the mated female wasp fed more nymphs than the unmated female wasp did within the same biotype. The developmental duration of wasp for eggpupa (7.2±0.1 d) and pupa (5.2±0.1 d) on B biotype nymph was not significantly different from that on Q biotype (the corresponding time were 7.3±0.1 d and 5.6±0.1 d, respectively). The emergence rate of wasp pupae from B biotype nymphs (73.55%±1.42%) was not significantly different from that from Q biotype nymphs (68.42%±13.01%). The results suggest that E. sophia contributes to the displacement of B biotype by Q biotype of B. tabaci in the laboratory, but this effect left to be known in fields.

Key words: Encarsia sophia, Bemisia tabaci, biotype, parasitizing behavior, host preference