Evidence of Interspecific Competition Between Trialeurodes vaporariorum (Westwood) and Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) on Some Greenhouse-Grown Plants

Two whitefly species, sweetpotato whitefly (SPWF) [Bemisia tabaci (Gennadius)] and greenhouse whitefly (GHWF) [Trialeurodes vaporariorum (Westwood)], sometimes infest many greenhouse-grown ornamental plants at the same time, particularly during the early infestation period. Large cage, Petri-dish cage, and leaf clip-on cage experiments were conducted in greenhouses and temperature-controlled chambers to examine the competitive interactions of these two whiteflies on green bean (Phaseolus vulgaris L.) and poinsettia (Euphorbia pulcherrima Willd.). The results demonstrated that the two species do not coexist on the same leaf for a time period of longer than two generations (approximately 50–60 days), and that GHWF was the dominant species on green bean while SPWF was the dominant species on poinsettia. Shifts in species dominance between the two whitefly species were not affected by cage size, initial density, and constant temperatures of 20, 25, and 30°C. Dominance of one species over the other on a given host probably was related to reduced feeding and ovipositional activity by adults and reduced growth and possibly survivorship of immatures of the subordinate species on a less suitable host, although other factors may affect competitive interactions between the two species.