ECOLOGICAL STUDIES ON THE WHITEFLY, Bemisia tabaci (GENNADUIS)

Abstract

Distribution pattern of Bemisia tabaci (Gennadius) (Aleyrodidae: Homoptera-Hemiptera) were studied on cucumber varieties (Madin, Sweet crunch and Amera). Infestations of whitefly stages were estimated in cucumber field grown in early and late summer plantations during two successive seasons (1998/1999 and 1999/2000). All stages were sampled from the main stem nodes leaves of plant • variety to examine the distribution pattern of whitefly adults, eggs and larvae and pupae on cucumber plant. The results . showed significant differences among infestations to main stem nodes leaves. The greatest numebr of adults, eggs and larvae and pupae were recorded on the main stem nodes leaves 4-6, 8-10 and 9-11 respectively. Also, this study suggested that when collecting sampling leaves of cucumber plants in the field, only 10 leaves from ten plants are enough to be picked from each plot (1/50 feddan) from the main stem nodes leaves for each stage of whitefly to makes the best assessment of whitefly stages in cucumber plants. Based on Taylor's power law patchiness regressions, results indicated that, all stages whitefly were aggregated, but there were distinct degrees of aggregation between main stem nodes leaves. This changed slightly with stages, but was similar between cucumber plants.