White pine blister rust is a fungal pathogen from Eurasia. The fungus was accidentally transported to North America around the turn of the 20th century on shipments of seedlings from Europe. Canadian foresters interested in restoring clearcut areas imported seedlings from Europe to replant with. Unfortunately, instead of restoring forest resources, the seedlings unleashed a destructive pathogen into the environment.
White pine blister rust is incurable and it kills over 90% of all white pines (or five-needle pines) it infects. The fungus is dispersed by air, but it relies on secondary hosts of the Ribes or Castilea species - these include currants, gooseberries, and indian paintbrush. Wherever these plants are present, the fungus can spread and infect white pines.
Since the early 1900s, blister rust has been spreading steadily south from Canada. Forests in Canada, Washington, Idaho, Montana and Oregon - as well as on the East Coast - have been devastated in its wake. Blister rust is now an epidemic in California, including in the Lake Tahoe Basin.