A decline of coast live oak (Quercus agrifolia) has been observed
throughout southern California. In this study, the identity and pathogenicity of non-Botryosphaeriaceaefungal species consistently recovered from necrotic tissues of branch and bleeding trunk canker samples
from these locations were assessed.Species were identified morphologically and by comparison of the complete sequence of the internal
transcribed spacer (ITS) of the ribosomal DNA to sequences available
in GenBank. Phylogenetic analyses were then conducted using ITS and
partial sequences of the β-tubulin and mitochondrial small ribosomal
subunit genes for unknown species. Fungi recovered and identified
included Fusarium solani, Phaeoacremonium mortoniae, Diatrypella
verrucaeformis, and a fungus described herein as Cryptosporiopsis
querciphila sp. nov. One-year-old coast live oak seedlings were wound
inoculated under controlled conditions to test pathogenicity of the
fungal species. Each fungal species was successfully reisolated from
necrotic tissue at 70 and 100% for P. mortoniaeand all other species,
and xylem necrosis was significantly different between all treatments
and controls (P < 0.0001 at α= 0.05). Isolates of F. solani were the
most aggressive tested. These species represent new records of fungal
pathogens of coast live oak in California. Results from the pathogenicity test suggest that these fungi play a role in the decline of southern California coast live oak trees.