Efficacy of dimethyl disulfide (DMDS) for the control of chrysanthemum Verticillium wilt in Italy

Chrysanthemum Verticillium wilt caused by V. dahliae is one of the most damaging soil-borne diseases affecting chrysanthemum production in Italy and in Europe. After the definitive phase-out of methyl bromide and the non-inclusion or limitation of other fumigants a great deal of research to identify alternative treatments for controlling soil-borne pathogens has been conducted. One of the possible alternatives is the use of the new fumigant dimethyl disulfide (DMDS), which is also found in minor amounts in nature as a compound that plays a role in the global sulfur cycle. Two greenhouse trials were carried out over two years (2013e2014), to evaluate the efficacy of DMDS (600 kg ha1) on Verticillium wilt development and chrysanthemum stems yield in naturally infected soil. Treatment with DMDS significantly reduced the incidence of Verticillium wilt compared to the untreated control and results were similar to those obtained with a standard chemical fumigation (Chloropicrin or Metam sodium). Furthermore, stem yields obtained with DMDS and standard chemical fumigations were significantly higher than untreated control. This study shows that V. dahliae was not only isolated from diseased tissues, but also from symptomless tissues in residual chrysanthemum stems. Results suggest the importance of removing chrysanthemum residues infected with V. dahliae, for managing Verticillium wilt and the effectiveness of DMDS fumigation as well as standard chemical fumigations in decreasing V. dahliae residual stems colonization.