First report of Phytophthora cactorum and P. citrophthora causing root rot of Ribes lobbii in Oregon.
R. lobbii 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, two-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 3 initially asymptomatic plants developed symptoms after being sold and planted. Based on morphological characteristics, sequence analysis of the internal transcribed spacer region and pathogenicity tests, two causal agents were identified, namely P. cactorum and P. citrophthora. This is thought to be the first report of P. cactorum and P. citrophthora as root rot pathogens of R. lobbii.