Camellia flower blight is a disease characterized by visible lesions on the petals of Camellia flowers, which are infected by Ciborinia camelliae. Despite the fact that both the fungus and the host are native to Japan, there has been relatively little research on the ecological traits of the pathogen in nature. For this study, we aimed to determine the occurrence density and host preference of C. camelliae in the natural habitats of three species of Camellia spp., native to Japan; Camellia japonica, C. rusticana, and C. sasanqua. To this end, we selected five sites out in the wild, for each tree species, and counted the number of ascocarps and sclerotia on the forest floor. We also isolated the fungus from living and fallen flowers. As a result, ascocarps and isolates from fallen flowers commonly occur at sites for C. japonica and C. rusticana, with no evidence of the fungus being present on C. sasanqua plants, in the Ryukyu islands. Additionally, sites of C. japonica had more ascocarps than sites of C. rusticana, indicating that C. japonica might be the preferred host for this fungus.

Since 1993, tree decline and witches' broom have been observed on Rhododendron kaempferi including the national natural monument tree, Ooyamatsutsuji, in Utsukushimori, Hokuto, Yamanashi, Japan. Witches' broom on branches and trunk were observed year-round. The abaxial side of young leaves on diseased branches was covered with white hymenia in June. The symptom was similar to Exobasidium leaf blister. Based on morphological observation and molecular analyses of rDNA-ITS and LSU regions, the fungus isolated from the symptoms was identified as E. pentasporium. This is the first report identified the causal agent of the witches' broom diseases in this area. It suggests that this epidemic disease may be one of the factors for the decline of the plants.