Laboratory experiments were conducted to determine the influence of two tomato (Lycopersicum esculentum Miller) varieties (‘Trust’ and ‘Floridade’) on the biology of two whitefly species, Bemisia argentifolii Bellows & Perring and Trialeurodes vaporariorum (Westwood), and the interactions of host plant and whiteflies on the biology and parasitization of two parasitoid species, Eretmocerus eremicus Rose & Zolnerowich (native) and Eretmocerus mundus Mercet (exotic). Natural mortality, developmental time, and fecundity of B. argentifolii were not significantly different from those of T. vaporariorum on either tomato variety. The two species of Eretmocerus responded differently to the whitefly hosts. Eretmocerus mundus developed significantly faster, produced more progeny, and had greater parasitism and rate of emergence in B. argentifolii than in T. vaporariorum. Eretmocerus eremicus performed similarly on both whitefly species except that its females deposited more eggs in B. argentifolii than in T. vaporariorum nymphs. Females of both parasitoid species emerging from T. vaporariorum were significantly larger than those emerged from B. argentifolii. Tomato variety had no significant effect on the two parasitoid species. Eretmocerus eremicus attack both whiteflies efficiently and it can be used as a single species for whitefly management.