Open blisters of Cronartium ribicola, photo by D. ConklinThe Dehiscent Peridium

Fungi of the genus Cronartium and their relatives are obligate parasites and often serious plant pathogens. The stem rusts cause cankers, galls, or flagging of many important conifer species. The blister rusts, in particular, are very damaging. Infection of a stem leads to localized necrosis (canker), rapid branch death (flag), crown loss (topkill), and mortality. Seedlings and small trees are killed quickly; large trees are subject to reproductive failure and early death. Disease outbreaks can have significant economic and ecological impacts.

Most of the native rusts are widely distributed and uncommonly seen; they have a minor ecological role. A few native rusts, however, are rare, endemic species which cause little damage and greatly enhance biodiversity. Some native rusts at certain times and places do increase to outbreak levels and thereby assume economic and ecological significance.

In North America, the invasive white pine blister rust (Cronartium ribicola) is the most important species. The outbreaks which followed introductions in the early 1900s had profound impacts on American forests and forestry. Where blister rust is established, it remains a dominant factor affecting species evolution, community dynamic, and ecosystem processes. Blister rust is spreading to new regions and capable of adapting to new hosts and environments with severe consequences.

The important questions are how do we:

The pages listed below are offered to promote an understanding of the issues involved, facilitate communication and cooperation, describe current research, and present recent findings. Links are provided on this page to images, bibliographies, publications, projects, and other sites.

Image Collection

Selected photographs and illustrations are documented and achieved in the Flagstaff Lab Image Database. Images are held in and being added to the Forest Pathology Collection (and other collections). These images are accessed through the Search Tool: Search collection Forest Pathology where subject contains stem rust, white pine blister rust, or ribes.

Annotated Bibliographies

Several annotated bibliographies are compiled to support ongoing research and manuscript preparation. Bibliographies are presented as PFD files and updated occasionally as needs develop and new, relevant publications are acquired. Suggestions for additional or replacement papers are very welcome.

WPBR Impact (1/3/02)
Selected publications on white pine blister rust history and management.

WPBR Distribution and Spread (1/2/02)
Selected publications for the study of white pine blister rust biogeography, epidemiology, and meteorology.

Ribes Ecology and Pathology (12/27/01)
Selected references for projects on Ribes identification and rust hazard.

Publications and Presentations

White pine blister rust.
Van Arsdel. 1981. [lecture notes and illustrations.]
A brief synopsis of blister rust biology, hazard, and control.

Impacts of White Pine Blister Rust
Geils. 2001. 12th USDA Research Forum on Gypsy Moth and Other Invasive Species. Annapolis, MD.
Illustrated presentation on history and impacts of blister rust.

Using infection decline curves in alternate host eradication control. (PDF)
Van Arsdel. 1979. [lecture notes.]
A short review and presentation on data from the Lake States on effective eradication control zone and use of a square root distance to model infection decline.

Climatic Distribution of Blister Rusts on Pinyon and White Pines in the USA. (PDF)
Van Arsdel and Krebill. 1995. 4th IUFRO Rusts of Pines Working Party Conference. Tsukuba, Japan.
A landscape and meteorological analysis of rust distributions in three Great Basin ranges based on observation and application of concepts developed in the Lake States.

Distribution of White Pine Blister Rust in the Sacramento Mts. of New Mexico. (PDF)
Van Arsdel, Conklin, Popp, and Geils. 1998. 1st IUFRO Rusts of Forest Trees Working Party Conference. 1998. Finland.
Initial observations on the distribution on blister rust in a new, developing outbreak and the relationship of disease on pine to proximity to certain species of Ribes.

A Preliminary Hazard Model of White Pine Blister Rust for the Sacramento Ranger District, Lincoln National Forest (HTML and PDF)
Geils, Conklin, and Van Arsdel. 1999. Research Note RMRS-RN-6.
Based on initial observations of rust distribution in the Sacramento Mts., a landscape model of rust hazard is proposed. Using a geographic information system (GIS) and data on elevation, plant association, and topographic position, three hazard zones are mapped across a forest district. The model projects that the southwestern white pine population is serious threatened over most of its range on the district.

Establishment of white pine blister rust in New Mexico. (PDF)
Geils. 2000. HortTech. 10(3):528-529.
Review of previous papers plus a brief presentation and synthesis of observations from vegetation plots and meteorology stations established in the Sacramento Mts.

Projects and Cooperators

Currently, forest pathology research at the Flagstaff Lab includes participation in a number of projects with various cooperators. This research and cooperation is described on the Projects page.

Other Sites (Links)

There are numerous web pages by various authors in the forms of pest leaflets, management guides, grower notes, class exercises, image collections, quarantine notices, and exotic pest alerts. These sites can be located with your favorite internet search tool. In addition, several sites of special interest are:

The Whitebark Pine Ecosystem Foundation at

The Minnesota Tree Improvement Cooperative projects on white pine blister rust research at

British Columbia Ministry of Forests, Forest Practices Code, Pine Rust Management Guidebook at

USDA Forest Service Rocky Mountain Research Station, Flagstaff Lab
Title: The Dehiscent Peridium
Author: Brian W. Geils
Updated: 1/7/2002
Go To: The Peridium