White pine blister rust (Cronartium ribicola) is an exotic disease to North America that affects all five-needle pines (such as sugar pine, western white pine, and whitebark pine). The five-needle pines of North America are among the most susceptible white pines to this disease. The USDA Forest Service's Pacific Northwest Region (Oregon and Washington) has had a screening and breeding program to develop resistance to the disease since the late 1950's. Since then, over 10,000 western white pine, sugar pine, and whitebark pine parent trees have been phenotypically selected in forests, screened for resistance, seed orchards established, breeding work begun to help further increase resistance, and resistant seed supplied to help meet the restoration and reforestation needs.
The USDI Bureau of Land Management (BLM) is a major cooperator, particularly for sugar pine, in the phenotypic selection of trees and development of seed orchards. Other cooperators have encompassed a wide array of public agencies, Indian nations, and large non-public organizations.
Objectives of the resistance program include identifying the amount and type of genetic resistance present in natural populations of western white pine, sugar pine, and whitebark pine and developing durable resistance to this exotic pathogen while retaining the broad genetic diversity within the species.
Common garden studies have helped identify patterns of genetic variation in sugar pine and western white pine and are used as a primary basis for delineation of breeding zones. Field plantings have helped validate resistance from the screening program, and to help monitor changes in virulence of Cronartium ribicola.
Genetic resistance is currently the major management tool available for helping to re-establish five-needle pines in many areas of Oregon and Washington. Until recently, many natural resource managers have been reluctant to use sugar pine or western white pine in restoration or reforestation, and these species were becoming smaller components in many forest ecosystems. The availability of seed from the resistance program has renewed optimism in planting sugar pine and western white pine and will help keep these species as viable components in the ecosystem.
Information on efforts to evaluate and develop resistance are being disseminated to scientific and public audiences through workshops and presentations and poster sessions at conferences and symposia.
For further information, see Dorena and Cooperator's blister rust related Publications and Presentations.
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For questions or comments contact rsniezko@fs.fed.us.