See:
Greenhouse Plants, Ornamental - Black Root Rot
Note Out of over a hundred samples there have been 5 that were diagnosed with black root rot by the OSU Plant Clinic.
The fungus can be found in the black root sections of this Buxus sempervirens 'Suffruticosa' bush.
OSU Plant Clinic image, 2012.
Above ground symptoms of discolored yellow leaves. (Marginal yellowing is normal for this cultivar.)
OSU Plant Clinic, 2020.
See:
Greenhouse Plants, Ornamental - Black Root Rot
Note Out of over a hundred samples there have been 5 that were diagnosed with black root rot by the OSU Plant Clinic.