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Rootstocks in Washington State winegrape vineyards: Effects on plant-parasitic nematodes and vineyard establishment

Michelle Moyer: Washington State University

<div>Management of plant parasitic nematodes in Washington State vineyards has been dominated by preplant soil fumigation. One practice that may mitigate economic loss due to nematodes is the adoption of nematode-“resistant” rootstocks; unfortunately, own-rooted vines are preferred in Washington given their ease of retraining after damaging winter cold events. There is little information on the performance of most rootstocks against northern root-knot nematode (<em>Meloidogyne hapla), </em>the main plant-parasitic nematode species in the state, and even less information on dual performance against dagger nematode (<em>Xiphinema sp.)</em>. In 2015, we established a trial evaluating currently-available rootstocks in a commercial vineyard undergoing replanting after 20+ years of production. The rootstocks were planted in replicated plots of fumigated (metam sodium), nonfumigated, and nonfumigated inoculated with <em>M. hapla</em>. Fumigation was only effective against <em>M. hapla </em>for the first 6 months after application yet it remained effective against <em>Xiphinema</em> for 2 growing seasons. Rootstocks were poor hosts for <em>M. hapla</em> relative to own-rooted <em>Vitis vinifera, </em>but all were acceptable hosts for <em>Xiphinema</em> sp.<em>.</em> Several rootstocks (e.g., Harmony, 1103P) had greater shoot biomass at the end of year 2 compared to own-rooted <em>V. vinifera</em>. The goal of this project is to understand the long-term performance of rootstocks and the impacts of nematodes on vineyard lifespan in Washington State.</div>