Washington Dept. of Natural Resources 2003 FH Highlights

Washington Department of Natural Resources

posted by:
USDA Forest Service
Pacific Northwest Region
Forest Health Protection

Washington Forest Health Issues in 2003

Washington Forests General Forest Conditions	Insects Fir Engraver Pine Bark Beetles Citrus Long-horned Beetle Western Spruce Budworm Douglas-fir Beetle Spruce Beetle Douglas-fir Tussock Moth Western Hemlock Looper Gypsy Moth Other Defoliators
Aerial Survey Overview Survey Results
Animal and Abiotic Drought Fire Bear Damage
Diseases Sudden Oak Death Swiss Needle Cast White Pine Blister Rust

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.

Girdling cankers are often resinous, especially main stem cankers, which eventually result in topkill. Branch flagging (retention of red needles on dead branches) is the most obvious symptom of white pine blister rust and is caused by girdling cankers that kill branches rapidly.

tree affected by WPBR

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.

Additional Information

WADNR Forest Health Home

Washington Department of Natural Resources

PNW Region Forest Health Protection