Mechanical transmission of Ralstonia solanacearum during flower and leaf removal has contributed significantly to the spread and severity of bacterial wilt of tobacco in the south-eastern USA. Mechanical topping and harvesting also coincide with the time period when maleic hydrazide (MH) is applied to arrest axillary shoot growth. Previous controlled environment and field studies have demonstrated that MH alters the severity of bacterial wilt, especially in relation to application timing. A controlled environment study was conducted to determine the effect of MH and other growth regulator chemicals including flumetralin, IAA, IBA and NAA on the incidence and severity of bacterial wilt. Plants (cv. K346) were grown under standard agronomic practices for South Carolina. Seedlings were transferred to 15 cm pots and grown in a greenhouse on a 12-hour photoperiod artificial light supplement until they reached 30 cm tall. Plants were transferred into a controlled environment chamber at 30 °C, 68% RH on a 12-hour photoperiod. The experimental design was a randomized complete block with 3 replications and then repeated. A pathogenic strain (isolate Y3) of R. solanacearum was cultured on tetrazolium amended nutrient agar, re-suspended in de-ionized water at Optical Density₆₀₀ = 0.2 = 10⁸ cells/ml and diluted to 2x10⁶ cells/ml for inoculation. The growth regulator treatments and a water only control were applied 4 days prior to inoculation with R. solanacearum by misting the leaves until wetness with standardized solutions of each treatment. R. solanacearum inoculation simulated mechanical flower removal using a scalpel to excise the apical bud, then by pipetting 100 µl of inoculum on to the cut stem. Plants were assessed every 3-5 days for disease severity starting 7 days post-inoculation and rated on a 0 to 5 scale (0 = no visible symptoms, 5 = complete collapse of tissue). Stem necrosis was recorded on a 0 to 5 scale at the final disease assessment date. MH application reduced stem lesions, leaf wilting and stem necrosis (P < 0.05). Leaf wilting was reduced by IBA application (P ≤ 0.05). Flumetralin did not reduce incidence or severity of mechanically transmitted R. solanacearum (P ≤ 0.05).