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One of the most commonly encountered plant-parasitic nematodes in eastern Washington Vitis vinifera vineyards is Meloidogyne hapla; however, limited research exists on the impact of this nematode on V. vinifera. The objectives of this research were to determine the impact of M. hapla on Chardonnay and Cabernet Sauvignon vine establishment and to determine the host status of V. vinifera varieties/clones predominantly grown in Washington to M. hapla. In a microplot experiment, Chardonnay and Cabernet Sauvignon vines were planted into soil inoculated with different densities of M. hapla; population dynamics of M. hapla and vine performance were monitored over 3 yr. In greenhouse experiments, several clones representing five V. vinifera varieties, Chardonnay, Riesling, Cabernet Sauvignon, Merlot, and Syrah, were evaluated as hosts for M. hapla. In both microplot and greenhouse experiments, white varieties were significantly better hosts than red varieties. In the greenhouse experiments, Chardonnay and Riesling had 40% higher reproduction factor values than Syrah and Merlot, however, all varieties/clones screened were good hosts for M. hapla (reproduction factors > 3). In the microplot experiment, M. hapla eggs/g root were 4.5 times greater in Chardonnay compared to Cabernet Sauvignon 3 yr after planting but there was no evident impact of M. hapla on vine establishment.

The most commonly encountered plant-parasitic nematodes in eastern Washington Vitis vinifera vineyards are Meloidogyne hapla, Mesocriconema xenoplax, Pratylenchus spp., Xiphinema americanum, and Paratylenchus sp.; however, little is known about their distribution in the soil profile. The vertical and horizontal spatial distribution of plant-parasitic nematodes was determined in two Washington V. vinifera vineyards. Others variables measured in these vineyards included soil moisture content, fine root biomass, and root colonization by arbuscular mycorhizal fungi (AMF). Meloidogyne hapla and M. xenoplax were aggregated under irrigation emitters within the vine row and decreased with soil depth. Conversely, Pratylenchus spp. populations were primarily concentrated in vineyard alleyways and decreased with depth. Paratylenchus sp. and X. americanum were randomly distributed within the vineyards. Soil water content played a dominant role in the distribution of fine roots and plant-parasitic nematodes. Colonization of fine roots by AMF decreased directly under irrigation emitters; in addition, galled roots had lower levels of AMF colonization compared with healthy roots. These findings will help facilitate sampling and management decisions for plant-parasitic nematodes in Washington semi-arid vineyards.