Any condition which results in poor root function can cause yellowing and death of hollies (Ilex). Examples include drought, root injury associated with recent transplanting, and root rot disease. Black root rot, caused by the fungus Thielaviopsis basicola, is frequently observed. The disease is found on Japanese holly, blue holly, and inkberry. Susceptible blue holly cultivars include: Blue Angel, Blue Maid, Blue Prince, Blue Princess, Blue Stallion, China Boy, China Girl, and Dragon Lady.
The first symptoms of black root rot include yellowing and marginal scorch of the foliage. Later, twigs or stems may die back and eventually the entire plant may die. The root system of the declining plant is stunted and decayed. Black lesions on the infected roots contrast sharply with the adjacent healthy white portions. Lesions may appear on the tips of feeder roots or elsewhere along the root.
