See:
Rhododendron - Phytophthora Root Rot
Note Out of dozens of samples there has only been one diagnosed with Phytophthora root rot by the OSU Plant Clinic.
This Ilex × meserveae 'Blue Princess' has crown and root rot due to Phytophthora sp. Note the cut made at the base of the plant revealing necrotic discolored tissue.
OSU Plant Clinic Image, 2016.
See:
Rhododendron - Phytophthora Root Rot
Note Out of dozens of samples there has only been one diagnosed with Phytophthora root rot by the OSU Plant Clinic.