US Forest Service Research and Development Newly Discovered non-Ribes Hosts for an Invasive Blister Rust in the Western USA - Rocky Mountain Research Station - RMRS - US Forest Service
Advanced | Site Map

  • Rocky Mountain Research Station
  • 240 West Prospect
  • Fort Collins, CO 80526
  • (970) 498-1100
USDA US Forest Service
Home > Research Highlights > Hosts for an Invasive Blister Rust
 

Newly Discovered non-Ribes Hosts for an Invasive Blister Rust in the Western USA

Invasive species are labeled as one of the USDA Forest Service's Four Threats to our National Forests. Invasive species are also targeted within the USDA Forest Service Strategic Plan to improve the health of the Nation's forests, and management of invasive species is part of a major effort within the Rocky Mountain Research Station. Invasive white pine blister rust is a devastating disease of western white pine (Pinus monticola), whitebark pine (Pinus albicaulis), and other 5-needle pines that is caused by the introduced fungus Cronartium ribicola. The rust completes its life cycle by alternately infecting pines and "non-pine" hosts. Ribes species (currants and gooseberries) were thought to be the only alternate host until 2004 when Moscow Forestry Sciences Laboratory scientists conclusively demonstrated that there are other natural alternate hosts of the white pine blister rust. In northern Idaho, infections resembling those of white pine blister rust were found on both sickle-top lousewort (Pedicularis racemosa) and scarlet Indian paintbrush (Castilleja miniata). Infections were then confirmed by DNA sequencing and artificial inoculations. Artificial inoculations also showed that the rust causing these infections was not specific to one host or alternate host. This summer, another paintbrush (Castilleja rhexifolia) was identified as a third potential host on the basis of artificial inoculations.

Natural infection of these alternate hosts may explain some shortcomings of the 50-year blister rust control program that attempted to interrupt the disease cycle by eliminating Ribes species, and cumulatively cost ca 1 billion in current US dollars. Renewed efforts to restore western white pine and whitebark pine within their historic range are underway. Of the original 5 million acres of white pine cover type in the Inland Northwest, only 5-10% still has a major component of white pine, largely due to being decimated by white pine blister rust. Whitebark pine is suffering a similar fate. Both western white pine and whitebark pine are keystone species. Past genetic research developed rust-resistant white pine and preliminary models for assessing rust hazard. With the current research focus on identifying hosts and host range, the Moscow Forestry Sciences Laboratory has broadened the scope of research on the invasive white pine blister rust fungus. Moscow scientists are now focusing on developing landscape-based models to assess rust hazard. This method will give managers a tool for choosing silvicultural methods for the restoration of white pine stands.

The discovery of new alternate hosts for blister rust and subsequent research at RMRS will undoubtedly impact rust research on other 5-needle pines in the western US--sugar pine (Pinus lambertiana), bristlecone pine (Pinus aristata), limber pine (Pinus flexilis), foxtail pine (Pinus balfouriana), and southwestern white pine (Pinus strobiformis). Understanding the potential behavior of the blister rust epidemic will help us restore impacted ecosystems.

For further information see: McDonald, G.I., B.A. Richardson, P.J. Zambino, N.B. Klopfenstein, and M.S. Kim. 2006. Pedicularis and Castilleja are natural hosts of Cronartium ribicola in North America: a first report. Forest Pathology 36:73-82.

Other white pine and white pine blister rust findings can be found at: http://forest.moscowfsl.wsu.edu/smp/html/white_pine_blister_rust.html

Rocky Mountain Research Station
Last Modified: Monday, 28 April 2008 at 17:16:46 EDT (Version 1.0.5)