The effects of physiological factors and host plant experience on the ovipositional activity of the sweet potato whitefly, Bemisia tabaci

Both egg load and levels of vitellogenin and vitellin increased when Bemisi a tabaci Gennadius (Homoptera: Aleyrodidae), were deprived of host plants. These increases resulted in significant increases in rates of oviposition. There was no difference in total fecundity between whiteflies temporarily d eprived of hosts and a control treatment that had continuous access to host s. The results of previous exposure to a preferred host, melon (Cucumis mel o), and a non-preferred host, cotton (Gossypium hirsutum), were also examin ed. B. tabaci deposited significantly more eggs during a 6-h period on melo n than on cotton, regardless of host species they were previously confined to. In addition, whiteflies previously exposed to cotton, deposited more eg gs than females previously exposed to melon. This higher rate of ovipositio n resulted in a low egg load as well as lower levels of vitellogenin and vi tellin. Conversely, a low rate of oviposition led to high egg load and high levels of vitellogenin and vitellin. Individuals from the same treatment e xhibited variation in egg load, which was negatively and significantly corr elated with previous oviposition activity. We conclude that the effects of previous host plant exposure on oviposition were, in part, due to behaviora l differences that are not related to the reproductive physiology.