First Report of Phytophthora cactorum and P. citrophthora Causing Root Rot of Ribes lobbii in Oregon

Ribes lobbii (Gray) is a native, deciduous shrub from British Columbia, California, Oregon, and Washington that is grown for its pendulous red and white flowers, bristly fruit, and attractive, aromatic foliage. It is uncommon in nature and has only recently begun being propagated for sale in ornamental and native nurseries. In April 2013, 2-year-old containerized plants (15/50 plants) were found with severe wilt and chlorosis symptoms at a nursery production facility in western Oregon. Most fine roots were completely rotted and larger roots exhibited numerous black lesions. By the end of August, 50% of the plants were affected and most died within a few weeks of initial symptom development. At least three initially asymptomatic plants developed symptoms after being sold and planted. Isolation was attempted from 10 plants by plating pieces of necrotic root tissue (3 mm2) that had been surface disinfested for 1 min in 10% bleach and 1 min in 70% ethanol onto PARP medium (2). Eight Phytophthora isolates were...