Nematicidal Activity of a Garlic Extract Formulation against the Grapevine Nematode Xiphinema index

Abstract

The nematicidal activity of garlic extracts is known on root-knot nematodes but never investigated on the grapevine nematode Xiphinema index. In this study, the nematicidal activity of a commercial garlic extract formulate (GEF) was assessed on X. index, both in vitro and in a pot assay. In the in vitro assays, mixed specimens of X. index were exposed to a 0-4 mL L^-1 range of GEF concentrations, checking nematode immotility and mortality after 2, 4 or 8 h. In the experiments on potted grapevines, plants cultivated in soil infested by X. index were irrigated twice at a 15-day interval with 0.05, 0.2 and 0.5 mL L^-1 solutions of GEF, including nontreated soil as a control. An almost complete mortality of X. index specimens occurred after a 2 h exposure to a 2 mL L^-1 GEF concentration, while an 8 h exposure to even the 0.0312 and 0.0156 mL L^-1 solutions resulted in about 50% and 30% mortality, respectively. Soil treatment with a 0.5 mL L^-1 GEF solution significantly reduced the population of X. index and increased the grapevine root growth compared to nontreated soil or soil treated with the lower dosages. Results of this study indicated that garlic-based nematicides could be an effective tool for X. index management in organic and integrated vineyards.

Keywords: Xiphinema index; garlic extract; grapevine; sustainable control.

Figure 1

Effect of soil treatments with garlic extract formulation on soil population density of Xiphinema index on potted grapevine. Values are means of seven replicates ± standard errors. At each sampling date, bars marked by the same letters are not significantly different according to the Least Significant Difference Test (p ≤ 0.05).

Figure 2

Effect of soil treatments with garlic extract formulation on the potted grapevine plants in soil infested with Xiphinema index. Values are means of seven replicates ± standard errors. For each plant part, bars marked by the same letters are not significantly different according to the Least Significant Difference Test (p ≤ 0.05).