The effect of previous infestation (preconditioning) by the whitefly Bemisia tabaci (Gennadius) biotype B on the population fitness of subsequent infestations that fed on three isogenic tomato genotypes (wild-type [Wt], a jasmonic acid [JA] defense-enhanced genotype [35S], and a JA-deficient genotype [spr2]) was examined. We tested the hypotheses that whiteflies fed on preconditioned tomatoes (Solanum lycopersicum L.) would have reduced fitness and that the effect would be mediated via the JA-dependent systemic plant defense pathway. Preconditioning by the whitefly resulted in decreased levels of soluble sugars and free amino acids and increased salicylic acid (SA), total phenolics, and condensed tannins for all three genotypes. The durations of the larval and pupal stages were prolonged in whiteflies fed on the preconditioned plants compared with those that fed on control plants. Furthermore, preconditioning resulted in reduced fecundity and intrinsic rate of increase (r_m) of the whiteflies that subsequently fed on the three tomato genotypes. Whiteflies were more likely to feed and deposit eggs on control plants than on preconditioned plants. Our results indicate that preconditioning induced decreases in leaf nutrients and increased induction of an SA based defense that degraded the quality of the substrate as evidenced by an increased developmental time and reduced fecundity of whiteflies that subsequently fed on them.