Plant parasitic nematodes are microscopic, unsegmented roundworms that feed on plant roots by puncturing and sucking the cell contents with a needlelike mouthpart called a stylet. They live in soil and within or on plant tissues. Of the many genera of plant parasitic nematodes detected in soils from California vineyards, root knot, dagger, citrus, lesion, and ring nematodes are the most important ones. Other nematodes associated with grape in California include stubby root nematode, Paratrichodorus minor; spiral nematode, Helicotylencus pseudorobustus; and needle nematode, Longidorus africanus. Of these, only needle nematode has been found to be damaging to grapes in California. Pin nematode, Paratylenchus hamatus, is frequently found in vineyards but is not thought to cause damage to this crop.