Study on Host Selection of Encarsia Sophia between Bemisia Tabaci B-Biotype and Q-Biotype Nymph
|School||Nanjing Agricultural College|
|Course||Agricultural Entomology and Pest Control|
|Keywords||Encarsia sophia Bemisia tabaci biotype host preference host feeding behavior functional response|
B and Q biotype are two very important Bemisia tabaci biotypes, and has invaded China and caused seriously damage. In recent years, it’s emerged that Q biotype B. tabaci has become the dominant biotype in the field in many areas, however, the role of parasitoids in displacement of B biotype B. tabaci by Q biotype in field left to be understood. In this paper we observed the parasitizing behavior and preference, host feeding behavior, functional response of Encarsia sophia on B and Q biotype B. tabaci and investigated the effects of B. tabaci biotypes on development, longevity and fecundity of E. sophia in the laboratory under 27±1℃, L:D=16h:8h and RH70～80%. The main results are as following.(1) The parasitizing process of E. sophia on B and Q biotypes B. tabaci nymphs were similar, including outside host examination, inside host examination and oviposition. Time for outside host examination of E. sophia was not significantly different between two whitefly biotypes, whereas the inside host examination and oviposition time on Q biotype nymph was significantly longer than that on B biotype nymph (190.2±14.6s vs 140.0±7.5s). In non-choice test, the number of Q biotype parasitized (8.1±0.5) and the total egg number (9.3±0.6) laid by E. sophia was significantly more than those,6.3±0.5 and 7.0±0.6, separately, for B biotype nymph, while the number of egg loaded per nymph parasitized were not significantly different between B and Q biotypes. In choice test, the number of nymph parasitized (3.1±0.4), total egg laid per wasp (3.8±0.5), and egg loaded per host (1.2±0.1) for B biotype was more than that corresponding number (1.8±0.3, 1.8±0.4 and 0.7±0.1) for Q biotype.(2) The developmental duration, emergence rate, longevity and fecundity of parasitoid are important indicators for weighing host fitness. 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 corresponding time 7.3±0.1 d and 5.6±0.1 d on Q biotype. Emergenece rate of wasp pupae from B biotype nymph (73.55±1.42%) was not significantly different from that from Q biotype nymph (68.42±13.01%). The average longevity (17.1±0.8 d) and lifetime fecundity (73.3±3.5) of the first generation E. sophia reared on B biotype B. tabaci was not significant different from that 16.0±0.7 d and 67.9±3.0, respectively, of E. sophia reared on Q biotype B. tabaci.(3) In spite of the mating of wasp or host biotype, host-feeding process of E. sophia were similar and could roughly be divided into the following three steps:①outside host examination,②ovipositor drilling and inside host examination,③pulling out the ovipositor and feeding host. Time for outside host examination of mated or unmated E. sophia was similar between on B and Q biotypes B. tabaci. Ovipositor drilling and inside host examination time wasn’t affected by whitefly biotype, but ovipositor drilling and inside host examination time of mated parasitoid on Q biotype whitefly nymphs was significantly shorter than that of unmated parasitoid. The feeding time of E. sophia was not significantly different between two whitefly biotypes, but feeding time of the mated parasitoid was significantly longer than that of unmated parasitioid. There were no significant differences in number of nymphs fed by E. sophia between B and Q biotypes, but the mated female wasp fed more nymph than unmated female wasp did within the same biotype.(4) Both numbers of nymph parasitized and that fed by E. sophia increased with host density for two biotypes. In each host density, host-feeding of parasitoid wasn’t affected by whitefly biotype, but there were significant effects of B. tabaci biotype on number of host parasitized. Functional responses of E. sophia could be described well by HollingⅡtype equation on both B and Q biotypes B. tabaci, and the model for B biotype was Na=1.2485Nt/(1+0.0634Nt) and Na=1.1189Nt/(1+0.0648Nt) for Q biotype. The maximum number of B and Q biotype B. tabaci parasitized and fed reached 19.7 and 17.2, respectively, within 24 h.(5) In different B. tabaci biotype B-Q ratio combinations, the number of B and Q biotype whiteflies parasitized and fed by E. sophia increased with the number of two biotypes whitefly supplied; the number of Q biotype B. tabaci parasitized and fed by E. sophia were not significantly different among combinations with same number of Q biotype B. tabaci; whereas the number of B bitotype B. tabaci parasitized were significantly different among the combinations with same number B biotype supplied, but the number of nymph fed by E. sophia were similar. When B:Q was 1:1,2:1,3:1,4:1,5:1, the number of nymph parasitized for B biotype was more than that number for Q biotype; when B:Q was 1:2 or 1:3, the number of whitefly nymphs parasitized by E. sophia between two biotypes didn’t differ significantly; when B:Q was 1:4 or 1:5, the number of Q biotype whitefly nymphs parasitized by E. sophia was significantly more than that of B biotype nymphs parasitized.