Field Performance of Winegrape Rootstocks and Fumigation during Establishment of a Chardonnay Vineyard in Washington

In Washington, most winegrapes are own-rooted Vitis vinifera, which is susceptible to the plant-parasitic nematodes Meloidogyne hapla and Xiphinema americanum. Using resistant rootstocks to manage nematodes has not been evaluated in Washington vineyards. A long-term vineyard trial was established to evaluate the effects of soil fumigation and rootstock genotype on M. hapla and X. americanum population dynamics and vine growth during vineyard establishment (first three years) in a replant scenario. Vines in an existing V. vinifera Chardonnay vineyard were first treated with foliar glyphosate in fall 2014. Randomized areas within the vineyard were then either fumigated or not with drip-applied metam sodium. Following fumigation, vines were removed. In spring 2015, the vineyard was replanted to Chardonnay on the following rootstocks: 1103 Paulsen, 101-14 Millardet et de Grasset, Teleki 5C, and Harmony. Self-grafted and own-rooted Chardonnay were included. Fumigation reduced M. hapla soil second-stage juvenile (J2) population densities on own-rooted and self-grafted vines for only the first year postfumigation. One year postfumigation, the self-grafted and own-rooted vines had higher population densities of M. hapla J2 than rootstocks. All rootstocks supported measurable densities of M. hapla J2 but were poor hosts relative to V. vinifera. Fumigation effectively reduced population densities of X. americanum for up to 3.5 years. Fumigation also reduced early establishment pruning weights. Vines grown in fumigated areas had lower pruning weights through year 2, but rootstock was the bigger influence on pruning weights by year 3. This trial demonstrates that rootstocks have a more sustained impact on nematode reestablishment and subsequent vine health in a vineyard replant scenario than that of preplant fumigation.