Distribution of Trialeurodes vaporariorum and Bemisia tabaci (Homoptera: Aleyrodidae) on Some Greenhouse-grown Ornamental Plants

The within-plant and between-plant distributions of all stages of both greenhouse whitefly (GHWF), Trialeurodes vaporariorum (Westwood) on poinsettia, chrysanthemum and gerbera daisy, and sweetpotato whitefly (SPWF), Bemisia tabaci (Gennadius) on poinsettia, were examined using Taylor's power law (s2 = amb) and Iwao's patchiness () methods. We found that all developmental stages of the two whitefly species on all plants examined were aggregated within and between plants. The vertical distribution of whitefly stages is stratified among leaves within the plant with respect to leaf age rather than relative height of the leaves on the plants. Most of the adults, eggs and the first-instar nymphs occurred on young leaves. The second- and third-instar nymphs occurred on middle-aged leaves, and most of the pupae and empty pupal cases occurred on middle-aged and older leaves. Comparison of whitefly counts from the different combinations of top, middle, and bottom leaves with the whole-plant counts on poinsettia was correlated and these leaves can be sampled as an indication of population levels within a greenhouse population.