Understanding the relationship of parasitoids with their insect hosts and crop plants is needed to develop good management strategies for Bemisia tabaci (Gennadius), a whitefly pest. The abundance and establishment of parasitoids of B. tabaci B-biotype were tested with taxonomically diverse plants in the greenhouse (7 plant species) and in the field (16 plant species in Egypt). Greenhouse tests were conducted on plants free of whitefly nymphs to avoid this influence on parasitoid behavior, and field tests were conducted in crops with feral populations of B. tabaci. In the greenhouse, the parasitoid, Encarsia pergandiella Howard, was most abundant on Vigna unguiculata (L.) Walpers, followed by Gossypium hirsutum L. The propensity for this parasitoid to forage on the bottom leaf surface compared with the top surface varied among crops (45–90% were on the bottom leaf surface) and over time (≈50% were on the bottom leaf surface around sunrise, whereas ≈90% were on the bottom surface by mid-day). Inundative releases of laboratory-reared parasitoids, Eretmocerus mundus (Mercet), into field crops increased parasitization rates in all crops tested. Some crops (e.g., two Brassica species and V. unguiculata) were more conducive to parasitism of B. tabaci than other crops (e.g., Cucumis sativus L. and Lycopersicon esculentum Miller). Findings from this research may be useful in the enhancement and conservation of parasitoids of Bemisia.