From 2002 through 2004, most insect and disease damage agents in Utah increased significantly, in some cases to epidemic levels. Although there are many potential causes for these large increases, the most significant contributing agent is drought. The extended drought throughout the Intermountain Region lowered tree resistance to insect attacks or infections caused by diseases. Once insect populations reach epidemic levels, insect disturbance becomes a stand-replacing event often leading to widespread tree mortality similar to wildfire. If advance regeneration occurs within stands affected by the epidemic, stands will eventually recover.
Matthews, K., DeBlander, V., Pederson, L., Mocettini, P. and Halsey, D. (2005). Utah forest insect and disease conditons report 2002-2004. USDA Forest Service, State and Private Forestry, Forest Health Protection, Intermountain Region, R4-OFO-TR-05012, 58 pp.