The plant-parasitic nematode Meloidogyne hapla (northern root-knot) is damaging to Vitis vinifera in the Pacific Northwest (PNW). While nematode-resistant rootstocks are available, they are rarely used in the PNW. Previous greenhouse studies indicate that rootstocks are poor hosts for M. hapla compared to own-rooted V. vinifera. To further explore the use of rootstocks for M. hapla management, two additional trials were conducted. In the first trial, six rootstocks (101-14 Mtg, Harmony, 1103P, Teleki 5C, and own-rooted grafted and ungrafted Chardonnay) were planted in spring 2015 into either fumigated or nonfumigated areas of a vineyard in Patterson, Washington. In nonfumigated areas, a subset of vines was inoculated with M. hapla. Soil was sampled in the spring and fall for M. hapla. Fumigation initially controlled M. hapla, but populations began to rebound by October 2015. Own-rooted Chardonnay in nonfumigated, inoculated plots had significantly higher M. hapla population densities than in the fumigated plots. Rootstocks 101-14, 1103P, and 5C did not have statistically different nematode population densities between fumigation treatments, but Harmony had significantly more M. hapla in inoculated treatments. The second trial was conducted in the greenhouse. Four rootstocks (Harmony, Riparia Gloire, 3309C, and St. George) and an own-rooted Chardonnay control were challenged with four populations of M. hapla originally collected from vineyards in Oregon and Washington. Potted vines were inoculated with three M. hapla eggs/g soil. At the end of the experiment, vines were assessed for eggs per gram root and reproductive factor. Own-rooted Chardonnay had a high reproductive factor (50), while all rootstocks had reproductive factors below 1. This low reproduction factor indicates that these rootstocks are poor host for M. hapla populations. These combined results suggest that if rootstocks are considered in the PNW, selecting those with resistance to M. hapla may improve management options.

Funding Support: Washington State Wine and Grape Research Program