Control of the root-knot nematode Meloidogyne incognita by Dimethyl Disulfide (DMDS) applied in drip irrigation on melon and tomato in Apulia and Basilicata (Italy)

The effectiveness of different rates of Dimethyl disulfide (DMDS) applied to the soil in drip irrigation was tested against the root-knot nematode Meloidogyne incognita in two plastic-house trials on melon and tomato in southern Italy. The trials were carried out in naturally infested sandy soils according to a randomized block design with 5 replicates per treatment. In both trials the DMDS EC formulation was applied at rates of 400 and 300 L/ha by drip irrigation with PVC drip lines covered with virtually impermeable film (VIF). DMDS treatments were compared with 1,3-dichloropropene (140 L/ha) and untreated controls. Plastic VIF were removed 2 weeks after fumigations. Melons and tomatoes were harvested 5 and 7 times, respectively, and the yields recorded. At the end of the crop cycles, the nematode attack on the roots was evaluated according to a 0-5 scale. Soil samples were collected in each plot to evaluate soil nematode population. All nematicidal treatments significantly increased marketable yields of melon and tomato in comparison to the untreated controls (0.48 and 0.16 kg/m2). In the melon trial both rates of DMDS (400 and 300 L/ha) did not significantly differ from each other (0.71 and 0.70 kg/m2, respectively) and from 1,3-D (0.70 kg/m2). The same pattern was observed in the tomato trial, in which 2.78 and 2.16 kg/m2 of tomatoes were recorded with the highest and lowest DMDS rates, respectively, in comparison to 2.78 kg/m2 in 1,3-D treated plots. In the melon trial, final nematode population densities in DMDS and 1,3-D treated plots (0.2 eggs and juveniles/ml soil) were significantly lower than that observed in the untreated control (1.7). In the tomato trial, the soil nematode population density observed in the untreated control (18.4 eggs and juveniles/ml soil) was significantly higher than those recorded in all DMDS and 1,3-D fumigated plots (1 eggs and juveniles/ml soil). Also, in both trials and in all treatments, root gall indices were significantly lower than those observed in the untreated controls with no significant differences among the fumigant treatments.