Since 1991, an increase in the populations of the whitefly Bemisia tabaci (Genn.) (Homoptera: Aleyrodidae) infesting vegetables and ornamental plants in some localities of São Paulo State, Brazil, has been observed. High densities of this insect were verified on tomato, broccoli, egg-plant and squash; in some cases, tomato and squash presented the whitefly-related disorders named tomato irregular repening and squash silverleaf. Weeds, mainly Sida rhombifolia L., Sonchus oleraceus L., Solanum viarum Dun. and Ipomoea acuminata Roem. & Schult., showed high whitefly colonization. At the Holambra county intensive colonizations were recorded on or-namental plants, mainly Chrysanthemum morifolium Ramat. and Euphorbia pulcherrima Willd. (poinsettia). Daily insecticide applications did not reduce the insect infestations. Other crops, such as bean and cotton, were also infested. The disorders and type of infestations are similar to what has been observed in the U.S.A. In this country, the ability of certain populations of B. tabaci to induce the silverleaf disorder of squash and to colonize poinsettia intensely, among other characteristics, has been used to distinguish the "poinsettia strain" or "B strain". However, based on genomic and crossing/mating behavior studies, some investigators have considered that these two strains represent different species. In view of the similarity of the infestations and disorders that are occurring in the U.S.A., and more recently in São Paulo State, it is very likely that the "B strain" (or the new species) has been introduced in Brazil.
Insecta; whitefly; Aleyrodidae; outbreaks; squash silverleaf; tomato irregular repening; poinsettia