烟粉虱生物型对浅黄恩蚜小蜂寄主选择及个体发育的影响

为探讨寄生蜂在Q型烟粉虱Bemisia tabaci替代B型烟粉虱的过程中是否起作用， 我们在实验室条件(温度27±1℃, 光周期16L∶8D, 相对湿度RH 70%～80%)下， 观察了浅黄恩蚜小蜂Encarsia sophia寄生B型和Q型烟粉虱若虫的行为， 研究了浅黄恩蚜小蜂对B型和Q型烟粉虱若虫的选择性、 烟粉虱生物型对浅黄恩蚜小蜂取食数量及个体发育的影响。结果发现， 浅黄恩蚜小蜂体外检测时间在B型和Q型烟粉虱若虫间差异不显著， 而寄生Q型烟粉虱若虫时的体内检测和产卵时间(190.2±14.6 s）显著高于寄生B型时所用时间(140.0±7.5 s)。在非选择条件下， 浅黄恩蚜小蜂寄生B型烟粉虱若虫的数量(8.1±0.5头)及总产卵量（9.3±0.6粒）显著高于仅提供Q型烟粉虱的寄生数量(6.3±0.5头)及总产卵量(7.0±0.6粒)； 而被寄生若虫单头着卵量在处理间差异不显著。在选择性条件下， 该蜂寄生B型烟粉虱若虫量(3.1±0.4头)、总产卵量(3.8±0.5粒)及被寄生若虫单头着卵量(1.2±0.1粒)都显著高于寄生Q型烟粉虱时的情况(1.8±0.3头、1.8±0.4粒、0.7±0.1粒)。被寄生蜂取食的B型与Q型烟粉虱数量间差异不显著， 但对于同一生物型而言， 交配过的雌蜂能够取食更多的烟粉虱若虫。以B型烟粉虱为寄主时， 浅黄恩蚜小蜂雌蜂卵-黑蛹(7.2±0.1 d)、黑蛹-羽化(5.2±0.1 d)的发育时间与以Q型烟粉虱若虫为寄主时的相应发育时间(7.3±0.1 d, 5.6±0.1 d)间无显著性差异。以B型烟粉虱为寄主时寄生蜂的羽化率（73.55%±1.42%）与以Q型烟粉虱为寄主时的羽化率（68.42%±13.01%）间差异不显著。这些结果表明， 虽然浅黄恩蚜小蜂发育时间、 羽化率在烟粉虱2种生物型间无显著差异， 但该小蜂倾向于B型烟粉虱若虫作为寄主， 而且， 以B型烟粉虱若虫为寄主时， 小蜂的产卵量和寄生若虫数量均增加。但田间浅黄恩蚜小蜂的存在是否有助于Q型烟粉虱成为B型和Q型混合种群的优势种群， 还需进一步研究。

Effects of Bemisia tabaci (Hemiptera:Aleyrodidae) biotype on host selection and development of Encarsia sophia (Hymenoptera:Aphelinidae)

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.