An integrated strategy for management of Phytophthora disease in a holm oak dehesa system

Abstract: Dehesa La Herrería (Sevilla, Spain) is a livestock ranching system where foci of decline and death of holm oaks were observed in recent years. A phytopathological diagnosis revealed a consistent association of decline with a root rot, with a 97% of trees (including asymptomatic ones) infected by Phytophthora cinnamomi, altough Pythium spiculum was also consistently isolated from a 20% of oaks. The woodland phytosanitary status worsened throughout the period autumn 2017 – spring 2019, both by symptoms development in initially asymptomatic oaks and by death of trees initially at different defoliation levels. A strategy for integrated disease management is proposed, with stopping pathogen dispersal towards zones free of disease as main objective, as well as avoiding the loss of more oaks into the foci. Management strategy includes several preventive cultural actions and treatments for asymptomatic tree protection, as well as the application of resistance inducers, with preventive and therapeutic effect, on diseased oaks.