Monitoring of Long-Lasting Effects of Fumigation with Dimethyl Disulfide (DMDS) on Root-Gall Index, Root-Knots, Other Nematode Populations, and Crop Yield over Three Protected Cucumber Crops in Bulgaria

In order to evaluate the long-term effect of the new fumigant DMDS and its potential to be a part of IPM of root-knot nematodes, a two-year experiment was conducted on cucumber in a greenhouse in Bulgaria. In the first year, DMDS was applied in comparison with farmer nematicide strategy and untreated control in the first cucumber crop. After two consequent catch crops—lettuce in the winter period—a second cucumber crop followed in spring–summer. In this crop, the DMDS effect was studied with no treatment and was integrated into the post-planting strategy with Trichoderma spp. and garlic extract at plots previously treated with DMDS. The effect of DMDS was followed until 450 days after fumigation. Nematocidal efficacy of DMDS was 96% and the yield increased 65.5% in the first cucumber crop, and 80% and 100% in the second cucumber crop, respectively, when nothing was done or a combined strategy with Trichoderma spp. and garlic extract was followed. The DMDS effect on 44 non-target soil nematode genera was also followed. The negative impact of the fumigation was limited in time as non-target nematode communities regained previous crop levels in five months during our study. Therefore, DMDS can be properly included in soil IPM programmes and appears very promising for the protected crop industry in Europe.