Effectiveness of dimethyl disulfide (DMDS) for management of root-knot nematode in protected tomatoes in southern Europe

The root-knot nematode (Meloidogyne spp.) is a major threat for protected tomato crops, with Meloidogyne incognita, Meloidogyne javanica and Meloidogyne arenaria being the most frequent species in southern Europe. This problem is critical for EU tomato growers, as effective fumigants have lost their registration and effective technical solutions are not available, except through national derogations. This paper gives a review of the efficacy of the new fumigant dimethyl disulfide (DMDS) against Meloidogyne spp. in protected tomato in southern Europe. A total of seven trials were carried out during 2012-2014 in Italy (3), Spain (2) and Greece (2) against root-knot nematodes, under conditions of medium-high levels of nematode infestation. The fumigant Accolade/Paladin. 94.1% EC (Arkema) was applied in drip chemigation, at 300 and 400 L ha(-1) and compared with 1,3-dichloropropene (1.3D; 120-200 L ha(-1) formulated product) and an untreated control. Before application, soil and chemigation lines were covered with virtually impermeable film (VIF). Twenty-one days after fumigation (14 days covered with VIF and 7 days left uncovered for soil aeration), tomato seedlings were transplanted. Evaluations of nematode infestations of the roots and of crop yield were made. The gall severity index (GSI) according to a 0(-1)0 scale showed medium-high root damage at harvest, with an average index of 5.3 observed in the untreated control. DMDS gave effective control of Meloidogyne spp. at both rates of application: GSI of 1.0 with 400 L ha(-1) and 1.3 with 300 L ha(-1). The standard treatment 1.3D (several tradenames) gave an average GSI of 1.4. DMDS greatly increased tomato yield when compared with the untreated control: by 62.7% for DMDS 400 L ha(-1) and 55.1% for DMDS 300 L ha(-1), whereas the average yield increase of the standard 1,3D was 61.5%. These results confirm the excellent efficacy of DMDS against root-knot nematodes in protected tomatoes.