The effects of 14 commercial sugars (arabinose, cellobiose, fructose, gentiobiose, glucose, inositol, lactose, maltose, mannitol, mannose, melibiose, sorbitol, trehalose, and xylose) (Sigma) on sweet potato whitefly survival were determined using in vitro bioassays. Of these, arabinose, mannose, and xylose were strongly inhibitory to nymphal development. When 10% mannose was added to the diet, very few nymphs developed to the 2nd instar (14.37%) and the 3rd instar (0.86%); development beyond the 3rd instar was not observed. When 10% arabinose was added, only 15.86% of the nymphs molted to the 2nd instar and development did not occur beyond the 2nd instar. Addition of 10% xylose completely terminated whitefly development, preventing the molt to the 2nd instar. With decreasing sugar concentrations, the inhibitory effect was significantly reduced. In the tests using whitefly adults, arabinose, inositol, lactose, mannitol, mannose, sorbitol, and xylose were highly insecticidal. As compared to the other sugars, mortality rates were greatest when arabinose, mannitol, mannose or xylose was added to the diet. Adult whiteflies survived for less than 2 days when fed on the diet containing 10% of any one of these four sugars. Lower concentrations decreased whitefly mortality. At concentrations less than 5%, the insecticidal effect of mannitol and mannose disappeared. Interestingly, whitefly adults lived significantly longer when fed on diets containing 1% mannose or xylose than when fed the standard diet (control). The mode of action of the inhibitory and/or insecticidal sugars is being investigated.