Plant-pathogenic fungi (PPF) as Verticillium dahliae and Phytophthora spp. are the main soil-borne diseases affecting olive. V. dahliae occurs worldwide, whereas Phytophthora spp. attacks olive in waterlogged soils. Prevalence of V. dahliae attacks ranges 35 to 71%. Up-to 87% tree-yield reductions can occur. The large dispersion of V. dahliae has occurred concomitant with both the expansion of the olive crop and the changes in cropping practices (e.g. use of self-rooted planting stocks, high-tree-density planting, drip-irrigation, reduced tillage, etc. in newly cultivated soils or fertile soils previously cropped with V. dahliae hosts).