Scientists analyzed tree-ring data from paired live and dead Engelmann spruce from the severe spruce beetle outbreak on the Markagunt Plateau in southwestern Utah. The data were collected from increment cores, which were sanded and cross-dated using the marker year approach and digitized using a microscope and a sliding stage. They found that the traumatic resin duct prevalence during the outbreak was significantly higher than over tree lifespans. All other metrics characterizing tree vigor, (diameter, age, ring width, and basal area increment), were not significantly different between live and dead trees. Forest Service scientists found that 90 percent of the live Engelmann Spruce exhibited traumatic resin ducts during a calendar year in close proximity to (1-3 years prior to or after) the date of death indicated by its paired dead tree that succumbed to mass attack during the spruce beetle outbreak. Forty percent of the dead trees exhibited traumatic resin ducts 1-3 years prior to their date of death. The prevalence of traumatic resin ducts over the lifetime of an Engelmann Spruce was exceedingly rare. Regardless of a tree’s live or dead status, 49 percent of all traumatic resin ducts occurred during the two decades of the spruce beetle outbreak. What was learned from this research is the inherent capability to produce traumatic resin ducts that can ‘pitch out’ attacking spruce beetles could be the primary mechanism by which Engelmann spruce survived the outbreak over the past two decades (1990s and 2000s). Because traumatic resin duct production in the sampled Engelmann spruce was exceedingly rare, this discovery represents a new line of tree-ring-based evidence that can be used to reconstruct other spruce beetle outbreaks.