Effects of Drip Irrigation on Population of Verticillium dahliae in Olive Orchards

Verticillium wilt of olive (Olea europaea L.), caused by Verticillium dahliae, is nowadays the most serious olive disease in Spain. The disease increments are being observed particularly in young olive plantations, favoured by several factors including inadequate cultural practices and crop production intensification, such as irrigation. Thus, three olive orchards affected by Verticillium wilt, with disease incidence ranging 30–50%, were selected to determine if the drip irrigation could favour the increase of pathogen in soil. Pathogen in soil was quantified in wet zones around the drippers and in dry zones out of them. Inoculum density in all experiments was higher in wet than in dry areas. After 4 months of watering, soil pathogen population increased considerably in wet and dry areas but inoculum density remained higher in the wet soil.