How Low Can They Go? Plant-Parasitic Nematode Distribution in a Washington Vineyard

Abstract

Summary Goals: To map the distribution of two plant-parasitic nematode species, the northern root-knot nematode Meloidogyne hapla and the dagger nematode Xiphinema spp., in a Washington State winegrape vineyard slated for replanting. These nematode species can reduce vineyard longevity and weaken or kill young vines. Knowing how these nematodes are spatially distributed in soil can improve implementation of management strategies. Key Findings: Northern root-knot nematode and dagger nematode had distinctly different distributions within the soil profile. Northern root-knot nematode was concentrated near the vine rows and drip-irrigation lines, in the upper 61 cm (24 inches) of the soil profile. This is reflective of its life strategy, in which association with fine roots and areas of moisture is essential. Dagger nematode was relatively evenly distributed at all distances from the vine row, and significant populations were found down to the deepest sampling depth of 122 cm (48 inches). This demonstrates that it can survive readily on hosts other than grape and can parasitize root types that are not parasitized by northern root-knot nematode. Impact and Significance: This work provides evidence for how and why nematode management practices may differ in their efficacy. Dagger nematodes were distributed throughout the sampled area and were found at depths that most fumigation efforts cannot reach. This increases the likelihood that dagger nematodes will recolonize treated areas, but this may take time as they move upward from deep in the soil. Root-knot nematodes may be more easily controlled via chemigation or fumigation, as their distribution corresponds to shallower areas with high fine root biomass wetted by drip irrigation.