Bacterial wilt caused by Ralstonia solanacearum is a highly destructive disease of flue-cured tobacco. Mechanical transmission of R. solanacearum during flower and leaf removal contributes significantly to the spread and severity of bacterial wilt and coincides with the time when maleic hydrazide (MH) is applied to arrest axillary shoot growth. Previous studies indicate MH can alter the severity of bacterial wilt based on application timing. The present field studies evaluated the effect of MH application on bacterial wilt development during flower and leaf removal. Plants (K346) were grown under standard agronomic practices. Plots consisted of rows 15.2 m long with a 1.2 m row spacing. The experimental design was a randomized complete block with four replications and repeated in time. Isolates of R. solanacearum were grown on nutrient agar and suspended in deionized water at 2x10⁶ cells/ml and used for inoculation. Royal MH-30 was applied at 1.5 gal/A in 50 gal of water. Plants were assessed weekly for disease severity and rated on a 0 to 5 scale. There were 4 treatments in the flower removal tests: inoculation with the bacterium without MH application; MH application 8 days prior to inoculation; MH application 4 days prior to inoculation; MH application immediately prior to inoculation. There were 5 treatments in the leaf removal tests: inoculation with the bacterium without MH application; MH application 14 days prior to inoculation; MH application 7 days prior to inoculation; MH application immediately after inoculation; MH application 4 days after inoculation. In the flower removal tests, the MH application 4 days prior to inoculation with R. solanacearum significantly reduced disease severity over the untreated, inoculated control and was the most effective treatment. In the leaf harvest tests, the MH application immediately after leaf removal showed significantly lower levels of disease than the other treatments. (Reprinted with permission)