Final Report: This is year 3 of a 3 year proposed project for the Washington Grape & Wine Research Program

Date: January 31, 2014

Project Title: Essential nematode data to enable decision-making by Washington grape growers

Principal Investigator(s): Michelle Moyer, Assistant Professor
Organization: WSU-IAREC, 24106 N. Bunn Rd., Prosser, WA 99350
Telephone: 509-786-9234

Principal Investigator(s): Inga Zasada and Paul Schreiner, Research Plant Pathologist and Plant Physiologist
Organization: USDA-ARS, HCRU, 3420 NW Orchard Ave., Corvallis, OR 97330
Telephone: 541-738-4021

Collaborators: Bill Riley, Viticulturist, Ste Michelle Wine Estates, Prosser, WA

Project Summary:

In two years of greenhouse evaluations of own-rooted Vitis vinifera varieties/clones, it was discovered that the white varieties (Chardonnay and Riesling) were better hosts for Meloidogyne hapla, the northern root-knot nematode, than red varieties (Syrah, Cabernet Sauvignon, Merlot). While all of the varieties/clones evaluated would be considered good hosts for M. hapla with reproduction factors (RF = final population/initial population) > 1, the magnitude of population increase was 4x greater on white varieties compared to red varieties. We also evaluated nine rootstocks (420A, 110R, 3309C, 101-14, Riparia Gloire, St. George, Harmony, Freedom, and Salt Creek) for host status to M. hapla. All of the evaluated rootstocks would be considered poor host for M. hapla with RF values < 1. In established wine grape vineyards in Washington we investigated the horizontal and vertical distribution of plant-parasitic nematodes. Two vineyards were sampled: a Chardonnay block on a sandy loam soil and a White Riesling block on a silt loam soil. The plant-parasitic nematodes M. hapla, Pratylenchus spp., Xiphinema spp., and Paratylenchus spp. were found at both vineyards while Mesocriconema xenoplax was only detected in the Chardonnay vineyard. At both vineyards, population densities of M. hapla were positively related to soil moisture and fine root biomass (p < 0.0001); however, these relationships were not always strong (r2 values ranging from 0.1 to 0.5). The same trend was observed for M. xenoplax at the Chardonnay vineyard (p < 0.0003; r2 = 0.1). The horizontal distribution of nematodes varied among the nematode genera with M. hapla and M. xenoplax concentrated in the row near emitters while Pratylenchus were aggregated at the vine row’s edges. At both vineyards, M. hapla and Pratylenchus population densities were concentrated in the upper 18” of the soil profile; this was true also for M. xenoplax in the Chardonnay vineyard. Conversely, Xiphinema was found throughout the soil profile at both vineyards. These results indicate that variety/rootstock selection may be an important tool for managing M. hapla and that there is potential to reduce the treated area within a vineyard when targeting M. hapla and M. xenoplax. The impact of plant-parasitic nematodes on vine productivity will continue to be explored in a newly established vineyard where grape varieties are being grown in areas with and without nematodes.

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Pest & Disease // Viticulture //