Phytophthora Rots of Apple and Pistachio

Fruit and nut trees are economically important crops in Arizona backyards or commercial orchards. The most common and most important diseases observed in fruit and nut trees are root diseases that cause a gradual and irreversible decline of the tree. Phytophthora rots of root, crown (rootstock) and collar (scion) are common and destructive diseases of fruit and nut trees worldwide. In Arizona, apple, pistachio, peach, and citrus are susceptible to Phytophthora rots, especially trees grown in heavy soils or under wet soils conditions resulting from excessive irrigation for extended periods.