EFFECTS OF SEASONAL AND SITE FACTORS ON XIPHINEMA INDEX POPULATIONS IN 2 CALIFORNIA VINEYARDS

Sampling of Xiphinema index for 2 years (1993-95) in two California vi neyards indicated that a greater number of nematodes occurred during t he winter months. The number of juveniles increased four-fold from Dec ember 1993 to January 1994, indicating a high reproductive rate during this time. Extremely high or low soil temperatures corresponded to lo w nematode numbers. Samples were taken from 0 to 31 cm and 31 to 62 cm deep both within and between the vine rows. Numbers of nematodes were greatest at the 0- to 31-cm depth in one vineyard with a loamy sand s oil, and at a depth of 31 to 62 cm in the second vineyard, which had a silt loam soil. In both vineyards, X. index population densities were greater within the vine row.