Bacterial wilt ( Ralstonia solanacearum ) is an extremely damaging disease of flue-cured tobacco. During the last 4 years (95-98), this disease accounted for over 50 % of all disease losses in South Carolina. This represents a dramatic increase from the previous four year period where losses from bacterial wilt accounted for only 16%. It is generally believed that infection of tobacco in the field occurs through the root system. The rapid spread of bacterial wilt within South Carolina suggests that the organism is being spread in a more rapid and efficient manor that would be expected solely by the movement of contaminated soil on equipment. The role of mechanical topping in the spread of bacterial wilt was evaluated in a randomized complete block factorial experiment where main blocks were method of flower removal (hand flower removal vs. mechanical topping) and subplots were tobacco variety (K326 vs. K346). The bacterium could be mechanically transmitted from a disease plant to a healthy plant with a mechanical topper (P < 0.001). Transmission of the bacterium and infection of tobacco plants following topping with a R. solanacearum contaminated mechanical topper ranged from 60% to 91% of the planting. Infected plants remained symptomless for 3-4 weeks following infection and then declined rapidly. Host resistance (K346) did not reduce the spread of the disease through mechanically topping when compared to a susceptible control (K326, P = 0.05). No bacterial wilt was observed in control plants that were mechanically topped without prior contamination of the cutter blades with R. solanacearum .