posted by: USDA Forest Service Pacific Northwest Region Forest Health Protection |
White Pine Blister Rust (WPBR) White pine blister rust is the most destructive disease of 5-needle (white) pines in North America. Since its introduction into Washington, it has caused widespread mortality throughout the range of its hosts. White pine blister rust infects all 5-needle pines, including western white pine and whitebark pine, and requires Ribes spp. as an alternate host. White pine blister rust causes cankers on branches and eventually the main stem of infected pines. Cankers on smooth-barked trees will often have a rough center surrounded by a diamond-shaped orange lesion of infected bark. On older trees with rough bark, the leading edge of infection is not apparent. Older cankers are rough and blistered in appearance.
This exotic disease has already decimated western white pine across much of its range to the extent that they are not well recorded by aerial survey. The surviving widely scattered western white pines are still dying, but do not often meet the threshold of groups of five or more trees. Washington's other five-needle susceptible host Whitebark pine grows in high elevation alpine areas. These trees provide a critical role in watershed protection and wildlife habitat. White pine blister rust has been slower to spread into these areas, but widespread infection is now occurring. Drought and blister rust have weakened whitebark pine to the point that mountain pine beetle is causing widespread mortality. Recent
surveys of the western white pine resource in Washington revealed
infection levels of up to 100% in some geographical regions. The Washington
DNR is currently performing a study of WPBR in juvenile white pine
(less than 5 years old) with increased genetic resistance to WPBR. |
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WADNR Forest Health Home Washington Department of Natural Resources PNW Region Forest Health Protection |