- Survey data compiled in 1995 showed that plant-pathogenic nematodes that cause yield loss in California and European vineyards are found in over 85% of Oregon vineyards. In over 37% of the samples collected, population densities of Xiphinema wnericanwn (dagger nematode) and Criconenw1la xenoplax (ring nematode) were greater than levels known to cause damage to grapes in California. However, high nematode densities were found in both areas of vigorous and stunted vines. Since nematode injury to mature perennial crops may becon-c evident only after a nurnber of years of parasitism, the potential losses from nematodes are unknown for the young winegrape industry in Oregon. Knowledge of the host-parasite relationship will be invaluable for assessing damage to grapevines and the long term impact of nematodes in Oregon vineyards. The relationship between nematode population densities and plant health also must be elucidated as a basis for interpreting nematode soil test results and advising growers. Currently, the sole nernaticide registered in Oregon for the control of plant-parasitic nematodes on grape is Nemacur. This and other nonfurnigant nernaticides did not consistently reduce nematode population densities nor significantly improve plant health in field trials conducted in Oregon during 1994 and 1995. More efficacious nernaticides and/or better application techniques are needed to mitigate the damage caused by nematodes in established vineyards. In addition, the use of soil amendments, ground covers that are antagonistic to nematodes, and biocontrol agents may have promise for the control of plant-par-dsitic nematodes. Ilese techniques also will be compatible with an integrated production system. Since young plants are generally more susceptible to nematode damage, we expect to see damage to vines planted on nematode-infested sites. As the industry moves to resistant rootstocks and new varieties, it will be necessary to develop methods to rid the soil of plant pests and pathogens. Promising techniques such as soil solarization and crop rotation need to be evaluated along with finding new ways to utilize soil fumigants in vineyard soils.