Application of Soil Solarization for Controlling Soilborne Fungal Pathogens in Newly Established Pistachio and Olive Orchards

There are two major soilborne pathogens that cause diseases in pistachio and olive orchards in Iran. These pathogens are Phytophthora spp. and Verticillium dahliae, which cause gummosis and wilting of trees and seedlings resulting in yield reduction. The population densities of Verticillium dahliae are high in new orchards that have been previously cropped to susceptible cultivars. Propagules of V. dahliae and Phytophthora spp. (P. pistaciae and P. dreschleri) were found at 900 to 1,600 CFU g −1 /soil in newly established orchards. Soil solarization was carried out in the studied areas to control these pathogens. After six weeks of solarization, the population density of V. dahliae was reduced from 1,600 CFU g −1 /soil to 300 in the orchard soils. This method decreased the incidence of disease up to 70% in the orchards.