The main target of this pathogen is the central vascular cylinder of the roots. The common symptom that gives "P. fragariae" the nickname of “red core rot” is the red discoloration of these roots. Due to the infection, the stele of the root turns a wine to brick red, and starts to decay and die from the tip upwards. Red color of the roots does not necessarily guarantee the presence of "P. fragariae" infection. The most dependable way to determine if a plant has "P. fragariae" is the presence of microscopic oospores. Another symptom of "P. fragariae" is badly rooted lateral roots, starting to turn a grey or brown color. Other roots are poorly developed. Root symptoms can be observed starting in late autumn, and young roots are particularly susceptible.