PARENT SESSION
Symposium #34: The Rapid Decline of White Pine Ecosystems of the West: Causes, Consequences, and Restoration Strategies.
Organized by: DF Tomback, AW Schoettle, and GI McDonald
Friday, August 9. 9:00 AM to 12:00 PM. Turquoise Ballroom, TCC.
The biogeography of blister rust invasions: the challenges of new outbreaks.
SMITH, ERIC*,1, GEILS, BRIAN2, KEARNS, HOLLY3, JACOBI, WILLIAM3, 1 USDA FOREST SERVICE, FORT COLLINS, CO2 USDA FOREST SERVICE, FLAGSTAFF, AZ3 COLORADO STATE UNIVERSITY, FORT COLLINS, CO
ABSTRACT- Within several decades of its introduction to western North America, white pine blister rust spread through western Canada, the Pacific Northwest states, into the Northern Rockies and down the Sierra Nevada. The rust has spread to the central Rocky Mountains and remote ranges in the Southwest, although much of this area has not yet been invaded. Although the invasion rate has declined, new disease outbreaks are expected whenever the rust is transported to areas with susceptible hosts and a suitable environment. The infestation severity, ecological impacts, and evolutionary consequences of these outbreaks may be anticipated from an understanding of the biology and ecology of the blister rust pathosystem in particular ecosystems. Such understanding provides opportunities for improved detection, mitigation, and management. We present our initial observations and hypotheses for new and expanding blister rust outbreaks in limber pine (Pinus flexilis) and southwestern white pine (P. strobiformis) of the central Rockies and the Southwest. Prospects for contined spread within these regions and to adjacent regions depend on establishment conditions. Both natural and dispersion processes and human transport may contribute to spread. We describe the distribution, ecology, and pathology of indigenous white pine and Ribes species in the uninvaded area of the western USA. Significant risks exist from white pines and Ribes cultivation for natural or horticultural purposes. Finally, we review how hazard ratings can be used in this complex system.
KEY WORDS: Cronartium ribicola , Pinus , Ribes , Biological invasion