Compounding effects of white pine blister rust, mountain pine beetle, and fire threaten four white pine species

A major decline in the abundance of whitebark pine (Pinus albicaulis Engelm.) has recently occurred in the United States, primarily as a result of white pine blister rust (Cronartium ribicola J.C. Fisch. ex Raben.). However, no information on the status of whitebark pine in British Columbia, Canada, was available. We sampled 54 subalpine stands in British Columbia, examining all whitebark pine trees within plots for evidence of blister rust and mountain pine beetle (Dendroctonus ponderosae Hopk.) damage. About 21% of all whitebark pine stems were dead, and blister rust was the most important agent of mortality. Of all living trees sampled, 27% had obvious blister rust infection (cankers), but actual incidence was suspected of being as high as 44% (using all evidence of blister rust). Blister rust incidence and whitebark pine mortality were significantly related to differences in stand structure and the presence of Ribes spp., but relationships with local climate and site variables were absent or weak. The lack of strong relationships with climate suggests favourable conditions for the spread of the disease throughout most of British Columbia. Very little evidence of mountain pine beetle was found. Overall, the prospects for whitebark pine in British Columbia do not appear good; a large reduction in population levels seems imminent.

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White Pine Blister Rust Severity and Selection of Individual Whitebark Pine by the Mountain Pine Beetle (Coleoptera: Curculionidae, Scolytinae)

Journal of Entomological Science ◽

10.18474/0749-8004-42.3.345 ◽

2007 ◽

Vol 42 (3) ◽

pp. 345-353 ◽

Cited By ~ 29

Author(s):

Diana L. Six ◽

Joel Adams

Keyword(s):

Moisture Content ◽

Mountain Pine Beetle ◽

White Pine Blister Rust ◽

White Pine ◽

Blister Rust ◽

Mountain Pine ◽

Pine Beetle ◽

Negative Effect ◽

Rust Severity ◽

Individual Trees

We investigated whether white pine blister rust (Cronartium ribicola) (J.C. Fischer in Rabenh.) severity, tree diameter at breast height (DBH), bark and phloem thickness, and sapwood moisture content influence the preference of the mountain pine beetle (Dendroctonus ponderosae Hopkins) for individual trees of whitebark (Pinus albicaulis Engelm.) and lodgepole pine (P. contorta Loud.). We measured these variables at 5 sites in Montana and Idaho and found a significant relationship between blister rust severity and attack of trees by D. ponderosae, with trees exhibiting greater blister rust severity being more likely to be attacked by the beetle. Sapwood moisture content was negatively correlated (P = 0.0004) with blister rust severity indicating that as severity increases there is an increasingly negative effect on water relations within the tree. Sapwood moisture content was significantly lower in P. albicaulis than in P. contorta at sites with beetle activity suggesting that there may be an interaction between blister rust severity and drought stress that, in turn, may affect beetle preference. DBH and bark and phloem thickness did not appear to influence beetle preference for individual trees. As blister rust spreads in P. albicaulis stands across the western U.S., this may translate to increasing levels of beetle-caused mortality in these areas.

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Whitebark and Foxtail Pine in Yosemite, Sequoia, and Kings Canyon National Parks: Initial Assessment of Stand Structure and Condition

Forests ◽

10.3390/f10010035 ◽

2019 ◽

Vol 10 (1) ◽

pp. 35 ◽

Cited By ~ 7

Author(s):

Jonathan C.B. Nesmith ◽

Micah Wright ◽

Erik S. Jules ◽

Shawn T. McKinney

Keyword(s):

Sierra Nevada ◽

National Parks ◽

Mountain Pine Beetle ◽

Whitebark Pine ◽

White Pine Blister Rust ◽

White Pine ◽

Blister Rust ◽

Mountain Pine ◽

Pine Beetle ◽

Foxtail Pine

The Inventory & Monitoring Division of the U.S. National Park Service conducts long-term monitoring to provide park managers information on the status and trends in biological and environmental attributes including white pines. White pines are foundational species in many subalpine ecosystems and are currently experiencing population declines. Here we present results on the status of whitebark and foxtail pine in the southern Sierra Nevada of California, an area understudied relative to other parts of their ranges. We selected random plot locations in Yosemite, Sequoia, and Kings Canyon national parks using an equal probability spatially-balanced approach. Tree- and plot-level data were collected on forest structure, composition, demography, cone production, crown mortality, and incidence of white pine blister rust and mountain pine beetle. We measured 7899 whitebark pine, 1112 foxtail pine, and 6085 other trees from 2012–2017. All factors for both species were spatially highly variable. Whitebark pine occurred in nearly-pure krummholz stands at or near treeline and as a minor component of mixed species forests. Ovulate cones were observed on 25% of whitebark pine and 69% of foxtail pine. Whitebark pine seedlings were recorded in 58% of plots, and foxtail pine seedlings in only 21% of plots. Crown mortality (8% in whitebark, 6% in foxtail) was low and significantly higher in 2017 compared to previous years. Less than 1% of whitebark and zero foxtail pine were infected with white pine blister rust and <1% of whitebark and foxtail pine displayed symptoms of mountain pine beetle attack. High elevation white pines in the southern Sierra Nevada are healthy compared to other portions of their range where population declines are significant and well documented. However, increasing white pine blister rust and mountain pine beetle occurrence, coupled with climate change projections, portend future declines for these species, underscoring the need for broad-scale collaborative monitoring.

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Effects of Disturbance on Tree Community Dynamics in Whitebark Pine (Pinus albicaulis Engelm.) Ecosystems

Forests ◽

10.3390/f9090566 ◽

2018 ◽

Vol 9 (9) ◽

pp. 566 ◽

Cited By ~ 5

Author(s):

Jeremy Amberson ◽

Megan Keville ◽

Cara Nelson

Keyword(s):

Tree Species ◽

Mountain Pine Beetle ◽

Pinus Albicaulis ◽

Whitebark Pine ◽

White Pine Blister Rust ◽

White Pine ◽

Blister Rust ◽

Tree Community ◽

Mountain Pine ◽

Pine Beetle

Whitebark pine (Pinus albicaulis Engelm.), an ecologically important tree species in high-elevation ecosystems of western North America, is threatened by white pine blister rust (Cronartium ribicola Fischer) and increased pressure from mountain pine beetle (Dendroctonus ponderosae Hopkins) due to climate warming. In addition, there is concern that fire suppression may be leading to successional replacement of whitebark by late-seral trees. Despite widespread knowledge that the tree is in decline, there is limited understanding of its successional dynamics, particularly in forests disturbed by white pine blister rust and mountain pine beetle. Our objective was to examine how disturbances have affected forest composition, structure, and seedling regeneration over a 22-year period (1990–2012) at 19 sites in the Cascade Mountains of Washington State (USA). Over that time, 13 sites (68%) were infected by white pine blister rust, 11 (58%) were disturbed by mountain pine beetle, and 5 (26%) experienced wildfire. Tree community composition changed significantly during the study period, primarily due to significant mortality of mature (≥20-cm diameter at breast height) whitebark pine. Despite loss of mature whitebark trees, we found little evidence of successional replacement by other tree species. Whitebark seedling density was unrelated to basal area of mature whitebark pine, but positively correlated with the presence of herb and shrub cover. Our results demonstrate the value of long-term repeated measurements for elucidating successional dynamics.

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Interactions of White Pine Blister Rust and Mountain Pine Beetle in Whitebark Pine Ecosystems in the Southern Greater Yellowstone Area

Natural Areas Journal ◽

10.3375/043.032.0105 ◽

2012 ◽

Vol 32 (1) ◽

pp. 31-40 ◽

Cited By ~ 25

Author(s):

Nancy K. Bockino ◽

Daniel B. Tinker

Keyword(s):

Mountain Pine Beetle ◽

Whitebark Pine ◽

White Pine Blister Rust ◽

White Pine ◽

Blister Rust ◽

Mountain Pine ◽

Greater Yellowstone Area ◽

Pine Beetle ◽

Greater Yellowstone

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Is Resistance to Mountain Pine Beetle Associated with Genetic Resistance to White Pine Blister Rust in Limber Pine?

Forests ◽

10.3390/f9100595 ◽

2018 ◽

Vol 9 (10) ◽

pp. 595

Author(s):

Christine Holtz ◽

Anna Schoettle

Keyword(s):

High Frequency ◽

Mountain Pine Beetle ◽

White Pine Blister Rust ◽

White Pine ◽

Resin Duct ◽

Limber Pine ◽

Blister Rust ◽

Mountain Pine ◽

Pine Beetle ◽

The Future

Limber pine (Pinus flexilis James) co-evolved with the mountain pine beetle (Dendroctonus ponderosae Hopkins; MPB) and is now also challenged by the non-native pathogen Cronartium ribicola (J.C. Fisch.) that causes the lethal disease white pine blister rust (WPBR). Previous research suggests that trees infected with WPBR can be preferred hosts for MPB. Using resin duct traits associated with MPB resistance, we tested for a relationship between resistance to MPB and WPBR in limber pine, in the absence of either biological agent. These analyses will help evaluate if MPB historically may have contributed to natural selection for WPBR resistance in advance of WPBR invasion, and could help explain the unusually high frequency of the dominant Cr4 allele for complete resistance to WPBR in limber pine populations of the Southern Rocky Mountains. Resin duct production, density and relative duct area did not differ between healthy trees previously inferred to carry the dominant Cr4 allele and trees that lack it at 22 sites, though some duct traits varied with elevation. MPB resistance does not appear to have played an evolutionary role in contributing to the high frequency of Cr4 in naïve populations, however, MPB may affect the future evolution of resistance to WPBR in the pines where the two pests coincide and WPBR will affect forest recovery after MPB epidemics. MPB-WPBR interactions in a changing climate will affect the future trajectory of limber pine.

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Changes in white pine blister rust infection and mortality in limber pine over time

Canadian Journal of Forest Research ◽

10.1139/cjfr-2013-0072 ◽

2013 ◽

Vol 43 (10) ◽

pp. 919-928 ◽

Cited By ~ 11

Author(s):

Cyndi M. Smith ◽

David W. Langor ◽

Colin Myrholm ◽

Jim Weber ◽

Cameron Gillies ◽

...

Keyword(s):

Mountain Pine Beetle ◽

Fire Suppression ◽

Basal Area ◽

White Pine Blister Rust ◽

White Pine ◽

Pinus Flexilis ◽

Limber Pine ◽

Blister Rust ◽

Dead Trees ◽

Pine Beetle

Limber pine (Pinus flexilis E. James) is under threat from white pine blister rust (WPBR), mountain pine beetle, drought, and fire suppression across its range in western North America. In 2003–2004, we established 85 plots to assess the mortality and incidence of WPBR on limber pine, and remeasured them in 2009. Infection was evident in 74% of the plots in 2003–2004 and 88% of the plots in 2009. The proportion of dead trees increased from 32% in 2003–2004 to 35% in 2009. The percentage of live trees infected increased from 33% in 2003–2004 to 43% in 2009. Mean live limber pine basal area in 2009 ranged from 0.03 to 77.8 m2/ha per plot. Twenty (24%) of the plots had no seedlings in the first measurement, but only 15% in the second measurement. Seedling infection was low (8% in 2003–2004 and 4% in 2009). In 12 plots that were measured three times, mortality increased from 30% of all trees in 1996 to 50% in 2003, then decreased to 46% in 2009. Infection decreased from 73% of live trees in 1996 to 46% in 2003, then increased to 66% in 2009. High mortality and infection levels suggest that the long-term persistence of many limber pine populations in the southern part of the study area are in jeopardy, and continued monitoring is needed to assist with management decisions.

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Climatic Correlates of White Pine Blister Rust Infection in Whitebark Pine in the Greater Yellowstone Ecosystem

Forests ◽

10.3390/f10080666 ◽

2019 ◽

Vol 10 (8) ◽

pp. 666 ◽

Cited By ~ 1

Author(s):

David P. Thoma ◽

Erin K. Shanahan ◽

Kathryn M. Irvine

Keyword(s):

Mountain Pine Beetle ◽

Greater Yellowstone Ecosystem ◽

Whitebark Pine ◽

White Pine Blister Rust ◽

White Pine ◽

Climate Conditions ◽

Rust Infection ◽

Blister Rust ◽

Mountain Pine ◽

Greater Yellowstone

Whitebark pine, a foundation species at tree line in the Western U.S. and Canada, has declined due to native mountain pine beetle epidemics, wildfire, and white pine blister rust. These declines are concerning for the multitude of ecosystem and human benefits provided by this species. An understanding of the climatic correlates associated with spread is needed to successfully manage impacts from forest pathogens. Since 2000 mountain pine beetles have killed 75% of the mature cone-bearing trees in the Greater Yellowstone Ecosystem, and 40.9% of monitored trees have been infected with white pine blister rust. We identified models of white pine blister rust infection which indicated that an August and September interaction between relative humidity and temperature are better predictors of white pine blister rust infection in whitebark pine than location and site characteristics in the Greater Yellowstone Ecosystem. The climate conditions conducive to white pine blister rust occur throughout the ecosystem, but larger trees in relatively warm and humid conditions were more likely to be infected between 2000 and 2018. We mapped the infection probability over the past two decades to identify coarse-scale patterns of climate conditions associated with white pine blister rust infection in whitebark pine.

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