Bacterial wilt (Ralstonia solanacearum) is an extremely damaging disease of flue-cured tobacco in North and South Carolina. Mechanical transmission of R. solanacearum on machine toppers, harvesters and stalk cutters has increased disease losses within North and South Carolina. Field trials conducted in R. solanacearum infested sites have shown that R. solanacearum can be easily spread during machine topping and harvesting in some fields but not others irrespective of the level of bacterial wilt within the field. R. solanacearum isolates, collected from tobacco fields, were selected to evaluate their ability to colonize tobacco stem tissue. Tobacco stems were inoculated with the R.. solanacearum isolates by misting bacteria of each isolate (106 cfu/ml) onto a simulated topper blade immediately prior to flower removal (topping). Disease development was evaluated 3-6 weeks following inoculation by rating field plots for disease on a 0 to 5 scale. Isolates differed in their ability to colonize stem tissues (P = 0.01) and could be divided into two groups; namely, stem colonizers and non-stem colonizers (disease index 3.3 - 4.9 and 0.1 - 0.2, respectively). Two stem colonizers and two non-stem colonizers were selected for root inoculation studies. All four isolates, both stem colonizers and non-stem colonizers, caused severe bacterial wilt disease when the bacterium was applied to roots at transplanting when compared to an uninoculated control (P = 0.01). The potential role of avirulence genes in R. solanacearum colonization of tobacco stem tissue will be discussed.