| Encarsia guadeloupae Viggiani (Hymenoptera:Aphelinidae) is a kind of important parasitic natural enemies of the spiraling whitefly, Aleurodicus dispersus Russell. The spiraling whitefly is widely known as a pest of vegetables, fruit trees, ornamentals and shade trees, which was first noticed as an invasive pest in2006in Hainan Province, China. Although E. guadeloupae has been used in biological control programs in some countries and regions, there is poor knowledge in the literature on its biology and ecology. Therefore, the aim of the present study was to understand some biological and ecological characteristics of this parasitoid. The main results were as follows:1) E. guadeloupae did parasitize the spiraling whitefly, but couldn’t parasitize Bemisa babaci.2) The morphological traits of E. guadeloupae at developmental stages were described in detail. The emergence and oviposition behavior of the adults were also observed. The adult emergence showed distinct diurnal rhythm,88.86%of the adults were emerged from8:00to16:00.3) E. guadeloupae could parasitize each nymphal instars of the spiraling whitefly, but showed no preference to different host instars in multiple-choice tests. Parasitism of E. guadeloupae was related to host-parasitoid ratio. The percentage parasitism decreased as host-parasitoid ratio increased. The percentage parasitism was61.37%,49.88%,34.72%, and22.50%respectively for the ratios of5,10,15, and30.4) Parasitized instars of the spiraling whitefly demonstrated greatly significant effects on development duration, adult longevity, and adult hind-tibia length of E. guadeloupae. The average development duration of the parasitoids reared from1st,2nd,3rd, and4th instar nymphs of the spiraling whitefly was24.94,23.50,23.35, and21.06days, respectively. For their adult longevity, the averages were1.09,1.22,1.75, and1.89days, respectively. The average of adult hind-tibia length was191.31,205.61,210.97, and200.89urn respectively for the parasitoids reared from1st,2nd,3rd, and4th host instars.5) Development durations of nymphal instars of the spiraling whitefly after being parasitized by E. guadeloupae did not change significantly, compared to those of normal host nymphs. Puparium size of the spiraling whitefly, however, was significantly affected by parasitization. The average of puparium size was0.47,0.51, 0.58, and0.55mm2respectively for the whiteflies being parasitized at1st,2nd,3rd, and4th instar by E. guadeloupae.6) Adult nutrition had significant effects on adult longevity of E. guadeloupae. The mean longevity of the adults fed with water was only2.67d. The adults lived significantly longer when provided with continual nourishment containing carbohydrate. The mean longevity of the adults feeding on20%honey water,10%honey water,10%sucrose water, and10%glucose water reached12.30,9.36,11.08, and6.63d, respectively.7) The development of E. guadeloupae reared on3rd instar nymphs of the spiraling whitefly was observed at26℃, and the time-specific life table of its experimental population was established. The average developmental duration was1.86,2.34,2.76,1.46, and8.35days respectively for1st instars,2nd instars,3rd instars, pre-pupae, and pupae. The parasitoids lived23.36days from egg to adult emergence. The average adult longevity was15.6days. The survival rate of the parasitoids at immature stages was62.38%. The mean fecundity was111.12eggs per female. Life table parameters were estimated as65.51for net reproductive rate (Ro),0.13per female per day for intrinsic rate of increase (rm),31.37days for mean generation time (T),1.14per female per day for finite rate (A),5.20days for population doubling time, and69.32for population trend index (I). |
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