47th TWC, Tob. Work. Conf., 2016, abstr. 69

Chemical management of blank shank in Georgia

University of Georgia, Statenville GA USA

Tobacco losses to black shank were higher in 2014 than any of the previous 20 years. Growers were left questioning the resistance of tobacco varieties and effectiveness of Ridomil Gold for management of black shank. Isolates of Phytophthora parasitica sent to North Carolina State university for testing were found very sensitive to mefanoxam, the active ingredient in Ridomil Gold. A new chemistry marketed as Presidio was available for use on tobacco for the first time in 2015. Trials were conducted at two locations to compare transplant water and layby treatments of Ridomil Gold and Presidio for control of black shank. At the Echols County location, disease distribution was very uneven, and may have affected the results. In this trial, plots receiving layby treatments of Ridomil Gold developed slightly less disease than the untreated plots while those receiving Presidio developed slightly more. However, final % black shank in neither Ridomil Gold treated nor Presidio treated plots differed significantly (p=0.05) from the untreated plots. At the Coffee County location, disease distribution was very uniform across the entire plot. In this trial, plots untreated at layby developed significantly (p=0.05) more black shank than plots treated with either Presidio or Ridomil Gold at layby. There was no difference in control (p=0.05) between Presidio and Ridomil gold. Presidio may offer growers another option for control of black shank but further testing is needed to find the best way to use it. (Reprinted with permission)