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

Dimethyl Disulfide (DMDS), as EC and AL formulation, was applied to control the vascular wilt fungus Verticillium dahliae in greenhouse experiments conducted in the two successive seasons of 2013 and 2014. The trials were carried out in Tuscany (Italy) on chrysanthemum cultivar “Veneri”, according to a randomized block design with 3 replicates per treatment. The soil of the sites was loamy and naturally infected by V. dahliae. DMDS was applied at the rates of 600 kg ha-1 via drip-irrigation (EC) or in shank application (AL). The treated plots were covered for 2 weeks with a very impermeable plastic film (VIF). After one week of soil aeration chrysanthemum seedlings were transplanted in each plot. DMDS treatments were compared with metam-sodium (1400 kg ha-1) or chloropicrin (500 kg ha-1) and non-treated controls and, at the end of the crop cycle, the effects of the treatments on disease incidence and crop performance were evaluated. The results showed a very good efficacy of DMDS against Verticillium wilt of chrysanthemum. In both trials, vascular wilt symptoms showed significant differences among untreated and treated plots (<1% compared with 51% untreated in 2013 and 0-6% versus 27% untreated, in 2014) with no difference among the treated plots. Treatments registered greater production in term of stem numbers per ground area and no difference occurred among them. Therefore, DMDS could be a new effective solution to control Verticillium wilt of chrysanthemum and because of its favorable ecotoxicologial profile, it could also be considered in sustainable floriculture programmes.