Invasive Shot hole Borers are an emerging and critical threat to the urban forests of Southern California. This boring beetle, from the group of beetles known as ambrosia beetles, drills into trees and brings with it a pathogenic fungus (Fusarium euwallacea), as well as other fungal species that may to help establish the colonies.
For more information:
Invasive Shot Hole Borers Quarterly Situation Report 10-17 to 12-17
http://ucanr.edu/sites/socaloakpests/Polyphagous_Shot_Hole_Borer/
http://eskalenlab.ucr.edu/handouts/pshb_symptomsandlookalikes.pdf