Whiteflies are inadvertently, but commonly, transported in international plant trade. Rapid, accurate identification is the essential first step when such insects are intercepted by quarantine authorities. Whitefly taxonomy, and identification, is almost entirely based on the fourth-larval instar or puparium, but often only the eggs, early larval instars or adults are detected. Morphological descriptions of the egg, first three larval stages and adult are presented for four species commonly detected in trade, Bemisia afer (Priesner & Hosny), B. tabaci (Gennadius), Trialeurodes ricini (Misra) and Trialeurodes vaporariorum (Westwood). Morphological characters are provided that enable most life stage/species combinations in these four species to be distinguished. The structure of the antenna is a reliable and simple character for separating the four larval instars. Phenotypic plasticity, previously only reported in the puparial stage, also occurs in the second and third-larval instars. Where morphological separation of two species is sometimes inconclusive, or impossible, identification can be achieved using four real-time PCR assays, designed and validated to distinguish between the four species. The assays are generic in their set-up and can be multiplexed to form two reactions allowing discrimination of B. afer and B. tabaci in one well, and T. ricini and T. vaporariorum in another.
Abstract. The whiteflies Trialeurodes lauri and T. ricini have been found to be moving in international plant trade. The taxonomic validity and separation of these species is relevant to the plant health quarantine services of the European Union as T. lauri is oligophagous, nor recorded as a virus vector and present in the EU, whereas T. ricini is polyphagous, reported to be a virus vector, and absent from the EU (except for the Canary Islands). Yet doubt has been cast on the validity of the two species, with the suggestion that T. lauri is merely a variant of T. ricini. The taxonomic relationship was therefore investigated using morphological and molecular data. One morphological character traditionally used for the separation of these two species, the arrangement of the submarginal papillae, was found to be unreliable but morphological differences between the two species were found in the cephalic setal state, body outline and dorsal pigmentation. However, the differences were subtle and not always reliable. The molecular data, based on the sequence of a fragment of the COI gene, support the hypothesis that T. ricini and T. lauri are distinct valid species.
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