 Several species of fungi infect the roots of waratahs, causing significant plant morbidity or death. Typical symptoms include yellow leaves, wilting, blackening and dieback or part or all of the plant, or lack of proteoid roots. The most common pathogen is the soil-borne water mold Phytophthora cinnamomi, which appears to be more problematic in cultivated plants than in wild populations. Mass plantings at the Royal Botanic Gardens in Sydney and at Mount Annan planted before the 2000 Summer Olympics were devastated by the disease. Rhizoctonia solani can cause damping off or root rot, and is an uncommon pathogen. Cylindrocarpon scoparium and C. destructans (now Nectria radicicola) are also uncommon causes of infection and result in decay of the crown of the plant. Although significant problems, fungi are less likely to be the cause of plant morbidity than poor drainage or soil conditions.
