Incidence and Population Density of Plant-Parasitic Nematodes Associated with Olive Planting Stocks at Nurseries in Southern Spain.

Nematode population densities were determined in 259 soil and root samples collected from 18 olive nurseries in Córdoba, Jaén, and Sevilla provinces (southern Spain), between October 1997 and May 1998. The most important plant-parasitic nematodes detected, in order of decreasing frequency of infestation (percentage of samples), were Mesocriconema xenoplax (39.0%), Pratylenchus penetrans (32.1%), P. vulnus (25.9%), Meloidogyne incognita (14.7%), M. javanica (11.2%), and M. arenaria (2.7%). No disease symptoms were noted on aboveground organs of infected plants. However, population densities of Pratylenchus and Meloidogyne spp. were at potentially damaging levels in most of the olive nurseries surveyed. Histopathological studies of galled roots from the naturally infected olive planting stocks showed a susceptible response to root-knot nematode infection. Large numbers of egg masses were present within the galled root tissues that might contribute to secondary infections. Feeding by root-knot nematodes induced the expected cellular alterations in the cortex, endodermis, pericycle, and vascular system, including giant-cell formation and the alteration of vascular tissues.