Written by S. Tianna DuPont, Tree Fruit Extension Specialist, Agricultural and Natural Resources, WSU; Shashika Hewavitharana, Associate Professor, Cal Poly; and Mark Mazzola, Research Plant Pathologist, USDA-ARS FS322E WSU Publications. March 2019. Download PDF Phytophthora rots can girdle the scion (collar rot), damage the rootstock just below the soil surface (crown rot), and cause necrosis and…