46th TWC, Tob. Work. Conf., 2014, abstr. 74

The use of maleic hydrazide to suppress mechanical transmission of Ralstonia solanacearum during leaf removal

Clemson University, Pee Dee Research & Education Center, 2200 Pocket Road, Florence, SC 29506, USA

Bacterial wilt disease caused by Ralstonia solanacearum is a major limiting factor in the successful production of flue-cured tobacco in the southeast U.S.A. Mechanical transmission of the bacterium during flower and leaf removal plays a significant role in the spread and severity of bacterial wilt and also occurs when maleic hydrazide (MH) is applied to arrest axillary shoot growth. Previous studies indicate MH can suppress the severity of bacterial wilt based on application timing. The present field studies evaluated the effect of MH rates and application methods on R. solanacearum establishment and disease development following mechanical transmission of the bacterium during harvesting. Plants (K346) were grown under standard agronomic practices. Plots consisted of rows 15.2 m long with a 1.2m row spacing. 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 for inoculation. Inoculation was performed by misting harvester defoliators and gleaners with isolate suspension before harvesting individual rows. Plants were assessed weekly for disease severity and rated on a 0 to 5 scale. There were 12 total treatments: an inoculated control; non-inoculated control; 3 different MH (Royal MH-30 EC) rate applications each with 4 different methods of application. Data collected suggest that lower rates of MH than the standard 1.5 gal/A application and MH application to stem tissue in addition to foliar sprays can reduce mechanical transmission of R. solanacearum during leaf harvest. (Reprinted with permission)