Inventory of white pine blister rust, fire, and bark beetles in sugar pine at Yosemite National Park
Mohr MD, Cribbs JE, Latimer A, Dudney J. 2025. Inventory of white pine blister rust, fire, and bark beetles in sugar pine at Yosemite National Park. Science Report. NPS/SR—2025/247. National Park Service. Fort Collins, Colorado. https://doi.org/10.36967/2308879
Invasive white pine blister rust (Cronartium ribicola, WPBR) threatens white pine populations throughout North America. Sugar pine (Pinus lambertiana), for example, has been declining in Sequoia and King Canyon National Parks (SEKI) due to WPBR, as well as other mortality agents, including fire, drought, and mountain pine beetle (Dendroctonus ponderosae, MPB). Whether these declines reflect population trends farther north in Yosemite National Park, however, is largely unknown. To this end, we surveyed 56 plots between June and October, 2023 in Yosemite. To test whether fire impacted WPBR or sugar pine recruitment, 23 plots were established in the Rim Fire footprint. Average extent (% of plots with ≥ 1 infection) and infection rate (% of all live stems with ≥ 1 infection) was 48.2% and 3.7%, respectively, though the extent was much lower in the Rim Fire plots (26.1%) compared to the primary plots (63.6%). Our generalized linear mixed models of infection rate suggested that fire and the presence of alternate hosts were important correlates of WPBR. As fire severity increased, WPBR infections declined, suggesting that high severity fire may dampen infection rates. Additionally, MPB was typically found in larger diameter stems, and the extent was higher in primary plots (54.6%) compared to the Rim Fire plots (30.4%). Recent surveys from SEKI show that sugar pine and WPBR infection rates are declining, likely due to complex interactions with drought, MPB, and fire. Comparable infection rates in Yosemite suggest that both sugar pine and WPBR may be following a similar trajectory. Though long-term monitoring is needed to quantify trends, our results underscore that restoration will help ensure the persistence of this ecologically important species.
- Type
- Published Report
- Authors
- Mohr, Michelle; Cribbs, Jennifer; Latimer, Andrew; Dudney, Joan
- Date of Issue
- 2025-03
- Publisher
- National Park Service
- DOI
- 10.36967/2308879
- Units
- IMD , NRSS , SIEN , YOSE
- Keywords
- 5-needle pine, drought, sugar pine, white pine blister rust