In separate experiments, Bemisia tabaci (Gennadius) from Namulonge, Uganda, was taken from a colony reared on uninfected cassava plants (Manihot esculenta) Crantz. (nonviruliferous whiteflies) and a colony reared on cassava plants infected with East African cassava mosaic virus (viruliferous whiteflies) and allowed to oviposit on uninfected and East African cassava mosaic virus-infected cassava plants for 3 d. There were no significant differences in the number of eggs oviposited and in the number of first instar, second/third instar collectively, and fourth-instar nymphs at different periods on the uninfected and infected plants. The number and sex ratio of eclosed adults as well as the total developmental period were also not significantly different between B. tabaci developing on uninfected or infected plants. These were the findings where either nonviruliferous or viruliferous whiteflies were allowed to oviposit on the plants. Highest mortality occurred on fourth instars developing on uninfected plants where either nonviruliferous or viruliferous whiteflies were allowed to oviposit. This was also the case on the infected plants, where oviposition was by viruliferous whiteflies. Based on regression equations, highest mortality on fourth instars was characterized as population density-independent. Mortality was highest on first instars developing on the infected plants where nonviruliferous whiteflies were allowed to oviposit, and was characterized as population density-dependent. A follow-up experiment showed no significant differences in the total number of nymphs and empty pupal cases over two generations for whiteflies developing on uninfected or infected plants. These data indicate that plants infected with East African cassava mosaic virus will not result in a population boost of B. tabaci. This is quite unlike what has been reported of plants infected with the putative recombinant virus involving East African cassava mosaic virus in combination with African cassava mosaic virus.
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Vol. 95 • No. 3