The Tahoe Daily Tribune is reporting that white pine blister rust (Cronartium ribicola) is on the move in the Tahoe Basin, the area surrounding Lake Tahoe in California and Nevada. The rust fungus, an introduction from Central Asia, attacks sugar pine, Western white pine, whitebark pine (commonly referred to as the "five-needle" pines), and many species of currants (Ribes spp.) as well. Once infected, the trees are weakened and can die from secondary infections, insect infestations, or from the rust fungus alone.
Given the difficulty of fighting a fungal invader, which can easily spread to new trees through tiny, wind-blown spores, scientists are instead focusing on the discovery of sugar pines that are resistant to the rust. A breeding program currently in progress aims to grow as many resistant seedlings as possible so that they can be planted throughout Tahoe Basin.
If you are curious about the origin and global spread of white pine blister rust, this PowerPoint presentation from Kim Hummer will provide you with all the details.