Several theories exist as to how a beetle finds a suitable tree to attack. The most basic theory is that a flying beetle lands on a tree for no particular reason and attempts to bore into it. Another theory is that stressed trees emit volatile compounds (turpenes). Bark beetles have evolved to detect these compounds and use them to identify suitable host trees. Another theory is that beetles can hear the water column in a stressed tree as it breaks when drought stressed. In the tree, this is also called hydraulic failure.
Jeff Schalau, Associate Agent, University of Arizona, and Tom DeGomez, Area Agent and Regional Specialist, University of Arizona
