An arborist reported an unusual pest found on an olive tree in Riverside CA late 2016. CDFA identified it as an Olive Bark Beetle (OBB) Phloeotribus scarabaeoides (http://blogs.cdfa.ca.gov/Section3162/?tag=olive-bark-beetle)
Currently, the pest status is Q (quarantined) but it is recommended to be changed to B.
The report states the OBB has been found at olive trees at grape vineyard as well as a residence and 3 nurseries, all in Riverside County. Surveys of olive trees at nurseries in other counties have not found any OBB.
The beetle is very small (2mm) and brownish-gray so it is difficult to detect. See https://www.forestryimages.org/browse/subthumb.cfm?sub=4146 for photos.
Current hosts are olive, Fraxinus spp., privet (Ligustrum sp.), lilac (Syringa), Phyllirea sp.
Damage is caused by larval feeding and then by adults on weakened stems and branches of causing decline and sometimes death
Damage can also be caused by adults creating feeding incisions on small, healthy branches causing the tips to dry out and die, or by adults damaging axillary buds when trying to initiate small galleries or holes where they can hibernate.
http://www7.inra.fr/hyppz/IMAGES/7030440.jpg
Good information about its biology and life cycle can be found on http://www7.inra.fr/hyppz/RAVAGEUR/6phlsca.htm