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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.

BackgroundBiological control provided by natural enemies play an important role in integrated pest management. Generalist insect predators provide an important biological service in the regulation of agricultural insect pests. Our goal is to understand the explicit process of oviposition preference, habitat selection and feeding behavior of predators in farmland ecosystem consisting of multiple crops, which is central to devising and delivering an integrated pest management program.MethodologyThe hypotheses was that maize can serve as habitat for natural enemies and benefits predators to provide potential to enhance biological control for pest insects in cotton. This explicit process of a predatory beetle, Propylea japonica, in agricultural ecosystem composed of cotton and maize were examined by field investigation and stable carbon isotope analysis during 2008–2010.Principal FindingField investigation showed that P. japonica adults will search host plants for high prey abundance before laying eggs, indicating indirectly that P. japonica adults prefer to inhabit maize plants and travel to cotton plants to actively prey on aphids. The δ13C values of adult P. japonica in a dietary shift experiment found that individual beetles were shifting from a C3- to a C4-based diet of aphids reared on maize or cotton, respectively, and began to reflect the isotope ratio of their new C4 resources within one week. Approximately 80–100% of the diet of P. japonica adults in maize originated from a C3-based resource in June, July and August, while approximately 80% of the diet originated from a C4-based resource in September.Conclusion/SignificanceResults suggest that maize can serve as a habitat or refuge source for the predatory beetle, P. japonica, and benefits predators to provide potential to enhance biological control for insect pests in cotton.