Forest Health Press Conference
January 22, 2010
Forest Health Aerial Survey Highlights
 
The aerial survey results revealed that more than a half-million new acres were infested in 2009; these are acres that
had not previously been affected by the mountain pine beetle epidemic.  The total number of acres impacted by the
entire mountain pine beetle outbreak since 1996 in Colorado and southern Wyoming is now 3.6 million acres; 2.9
million for Colorado and 700,000 acres for southern Wyoming.
 
•  The bark beetle infestation grew by 524,000 acres in Colorado and southern Wyoming in 2009. 
While logdepole pines continue to be the tree of choice, we are finding pockets of ponderosa and limber and
bristlecone pines infected as well. 
 
o  The most significant aspect of this year’s increase in the bark beetle epidemic is that most new activity is
east of the Continental Divide in northern Colorado and in the Snowy and Laramie Ranges of southern
Wyoming.
 
o  Larimer County experienced the largest increase, almost doubling in size in 2009 (from 280,000 to
500,000 acres).  The Medicine Bow and Roosevelt National Forests experienced the largest growth
330,000 acres (116,000 and 214,000 acres respectively).
 
There are four other emerging forest health concerns that the aerial survey recorded.
 
•  Spruce beetle outbreaks are most active in southern Colorado and kill high-elevation mature Englemann
spruce trees.  In 2009, 70,000 new acres of spruce mortality were detected in Colorado and southern Wyoming
bringing us to about 124,000 acres of current activity and a total of 508,000 acres over the course of the
epidemic.
 
Spruce beetles typically live in old spruce forests where scattered, wind thrown trees provide habitat for low-
level resident populations.  Once beetle populations reach epidemic levels, spruce beetles may attack and kill
spruce trees as small as five inches in diameter.  The current epidemic in southern Colorado started in 2002 and
is believed to be due to a combination of factors including large areas of dense, old spruce trees, a prolonged
drought and warm winters.
 
•  Aspen dieback, or sudden aspen decline, situation has stabilized.  All indications are that this condition
peaked in 2008 and expanded very little over the past year.  Our scientists believe that dieback and mortality of
large groves of aspen trees were mostly triggered by a long-term drought earlier in the decade.
 
•  Each year in Colorado, traps are placed throughout the state to detect the presence of gypsy moth and
emerald ash borer. Gypsy moth is a non-native pest that is found mainly in the eastern US.  In 2009, three gypsy
moths were detected along the Front Range.  Next month, a ground survey will be conducted to search for
presence of additional gypsy moths at those locations.
 
•  Thousand cankers disease of black walnut is the newest issue to Colorado, and is affecting black walnut trees
on the Front Range. Locally, we have had significant mortality in walnut trees. We continue to cooperate with
other states to study this disease and develop management strategies.