Bemisia tabaci biotype B considered as a separate species : Bemisia argentifolii
Bemisia tabaci (EPPO A2 quarantine pest) is a morphologically variable species. In USA, two populations have been distinguished : B. tabaci biotype A (cotton strain) found since 1897 and B. tabaci biotype B (poinsettia strain) discovered in 1986 which causes a plant disorder referred to as squash silverleaf. In California, US, authors have shown that B. tabaci biotype B is distinct from B. tabaci (biotype A) by crossing experiments, studies on intraspecific and interspecific mating behaviour, analysis of allozyme frequencies, PCR analysis of genomic DNA, and morphological characters. Morphologically, B. tabaci biotype B can be distinguished from B. tabaci biotype A in the fourth nymphal instar by the absence of a dorsal seta, the width of the thoracic tracheal folds, the width of the wax extrusions from the tracheal folds, and in the adult stage by migration distances of allozymes for three enzyme systems (phosphoglucomutase, phosphoglucose isomerase, esterase). The authors concluded that B. tabaci biotype B should be considered as a separate species Bemisia argentifolii Bellow ; Perring, n. sp. (proposed common name: silverleaf whitefly), and that a taxonomic revision of the whole genus Bemisia might be needed, as there is a possibility for a complex of species related to B. tabaci.
EPPO note: According to a paper from Bedford et al. (1992), B. tabaci biotype B is now found throughout the Mediterranean region, in South Africa, Caribbean, Central America and North America. In fact, it is probable that most outbreaks in glasshouses in Northern Europe involve this biotype. This point needs to be further investigated, and in particular the question is raised whether the concept of a new species (B. argentifolii) can be accepted by EPPO.
Bellows, T.S., Jr; Perring, T.M.; Gill, R.J.; Headrick, D.H. (1994) Description of a species of Bemisia (Homoptera: Aleyrodidae).
Annals of the Entomological Society of America, 87 (2), 195-206.
Bedford, I.D., Briddon, R.W.; Markham, P.G., Brown, J.K.; Rosell, R.C. (1992) Bemisia tabaci - Biotype characterisation and the threat of this whitefly species to agriculture.
Proceedings of the Brighton Crop Protection Conference - Pests and Diseases, vol. 3, 1235-1240.