The influence of white pine blister rust (Cronartium ribicola) on whitebark pine (Pinus albicaulis) in Mount Rainier National Park and North Cascades National Park Service Complex, Washington

Surveys to assess the status of whitebark pine (Pinus albicaulis Engelm.) populations, with respect to white pine blister rust (Cronartium ribicola J.C. Fisch.), were conducted in Mount Rainier National Park and North Cascades National Park Service Complex between 1994 and 1999. A total of 2173 whitebark pine trees and 1029 saplings were surveyed. Blister rust was documented in every stand, but rates of blister rust infections were highly variable (0% to 70%). Overall, 22% of trees were infected, 3 1% were dead, and 47% of all trees showed no signs of infection. Surveys of saplings (< 2.54 cm dbh) documented infection rates of 28%, mortality rates of 10%, and uninfected rates of 62%. Generally, the percent of trees that were infected increased from west to east and with increasing elevation. Mortality rates decreased with elevation, which may be a result of shorter growing seasons at higher elevations and a longer time period for the infection to spread within the tree. A long-term monitoring program, with permanent plots, has been established to track population status and to inform restoration programs.