Polysulfides Applied as Formulated Garlic Extract to Protect Tomato Plants against the Root-Knot Nematode .

The devastating root-knot nematode can cause severe damage to field and greenhouse crops. Due to high economic losses, alternative products are essential to replace banned or strictly regulated nematicides that affect human health and/or the environment. Garlic based products have been previously investigated as environmentally friendly nematicides and their active substances, diallyl polysulfides exist as formulated nematicides on the market. We tested the garlic-based nematicide NEMguard DE as protective of tomato roots. In vitro evaluation of the lethal concentration (LC) showed strong nematicidal activity with LC of 0.8 mg/mL after 96 h and LC of 1.5 mg/mL. NEMguard DE showed protective effect against as a single application in small pots and a second application further reduced root galling, significantly. Large greenhouse trials were carried out in two consecutive years to test single and monthly applications of NEMguard DE. In both years, no controlling effect could be observed on . We assume that the silt content of the loamy sandy soil used had an effect on the polysulfides, inhibiting their nematicidal effect. We conclude that further experiments are necessary to investigate the nematicidal potential of NEMguard DE under different soil compositions or as a different formulation.