[From the August 2015 issue of the UC IPM Green Bulletin] 

Declining coast live oak (Quercus agrifolia) trees have recently been found throughout urban landscapes in Los Angeles, Orange, Riverside, Santa Barbara, Ventura and Monterey counties. A fungus associated with a specific beetle is causing the decline by spreading what is known as “foamy bark canker disease” (Figures 1 and 2).

The fungal species, Geosmithia pallida, was recovered from symptomatic plant tissues in association with the western oak bark beetle...