SOB is an important causal agent of decline for coast live oak
in southern California. Throughout regions with oak mortality that
are GSOB-infested and -uninfested, several species of fungi have
also been recovered from symptomatic tissues of branch and bleeding trunk cankers of coast live oak in association to varying degrees with Diplodia corticola,a pathogen on coast live oak
(34,35). These fungi have not been reported to occur in association
with coast live oak and were also recovered in association with D.
agrifoliaand Dothiorella iberica (Botryosphaeriaceae), which are
pathogenic on coast live oak (35). The association between GSOB
and fungi is currently unknown at this stage of the research; however, it appears that GSOB is not an obligate vector for these species of fungi. This pattern of multiple fungi co-occurring with
Diplodia corticola has also been observed on declining cork oak
(Q. suber) in Europe (2,31–33,43). The occurrence of the previously unidentified fungi in the advancing margins of branch and
bleeding trunk cankers suggests that they may also be involved in
the decline of oak trees in southern California