| Bark beetles are a natural part of
the forest landscape. Every tree species can host a variety of bark
beetle species. Bark beetles typically attack vulnerable trees that
are weakened and stressed by disease, damage, drought or other environmental
factors. Healthy trees are able to defend attacks by flooding the
beetle entrance holes and under-bark galleries with pitch. The sticky
viscous fluid suffocates the beetle. Sometimes the pitch flows out
the same hole created by the beetle entrance. These blobs of sap
are often seen dotting the bark of an attacked tree.
The past century of fire suppression, the last thirty years of
restricted logging, and the past decade of drought have led to overcrowded,
stressed trees in our Arizona forests that are highly susceptible
to insect infestation. During the summer of 2002, bark beetle populations
in northern and sky island regions reached unprecedented levels.
Severe drought conditions led trees to decrease metabolic functions
to conserve water. Tree moisture levels declined and many trees
were unsuccessful at “pitching out” the onslaught of
bark beetles.
Large areas of beetle and drought killed trees present a problem
to land managers and homeowners as an increased fire threat and
as a falling hazard. If you suspect bark beetle damage in your trees
and would like more information, please link to the following page
from the Arizona Forest Health website for information on detection,
protection, and recovery (http://cals.arizona.edu/extension/fh/bb_prevention.html)
or you can e-mail us with questions or comments. Please see our
e-mail addresses at the bottom of this page.
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