Monitoring white pine blister rust in whitebark pine communities on the Sawtooth National Recreation Area, Idaho

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In 2005, the Sawtooth National Forest established a series of 8 plots to monitor white pine blister rust (WPBR; Cronartium ribicola) in high elevation whitebark pine communities within the Sawtooth National Recreation Area (NRA). The objective of the monitoring program was to determine the baseline level of WPBR infection and damage in whitebark pine stands on the Sawtooth NRA, and to be able to track changes in these levels over time. All 8 plots were resampled in 2013 and included a total of 453 overstory (>4.5’ tall) whitebark pine trees. This total consisted of 190 alive (42%) and 263 (58%) dead individuals. The density of alive overstory whitebark pine varied widely between plots, ranging from 14 – 380 trees/acre. In 2005, sampling included 452 individuals, with 402 (89%) alive and 50 dead (11%). Monitoring in 2013 found 4 plots (50%) with WPBR. Infection intensity ranged from 3% - 16% of alive overstory whitebark pine in the plots. Overall, active cankers were recorded on 8 trees, inactive cankers on 1 tree, and uncertain cankers on 5 trees. Based on the 9 active or inactive cankers, WPBR incidence for all alive overstory whitebark pine trees was 5% in 2013. In comparison, WPBR was recorded in 2 plots (25%) in 2005, with 1 tree infected in each of the plots. Overall, WPBR occurred on 0.5% of all alive overstory whitebark pine in 2005. One of the trees with an active WPBR canker in 2005 had an inactive canker in 2013. The other tree with an active canker in 2005 was recorded as “sick” in 2013, but without cankers. Eight of 9 trees with WPBR in 2013 were recorded as “healthy” in 2005. Analysis found the 2013 increase in WPBR incidence compared to 2005 significant (p<0.05). Blister rust cankers were not recorded on any whitebark pine ≤4.5’ tall in either 2005 or 2013. <br> All plots had less alive overstory whitebark pine in 2013 compared to 2005. Recent (since approximately 2004) mountain pine beetle (MPB; Dendroctonus ponderosae) accounted for nearly all the trees killed between the two sampling years and was the main mortality factor in all plots. Overall, the recent MPB outbreak killed 45% of all overstory whitebark pine trees sampled in 2013. Mountain pine beetle induced mortality varied substantially at individual plots, ranging from 9% - 87%. Most plots had <20% MPB mortality for overstory trees <5” dbh, but >50% mortality for trees >5” dbh. Analysis found the 2013 increase in MPB incidence compared to 2005 significant (p<0.05). One possible consequence of the large degree of recent MPB mortality is to reduce the usefulness of some plots to monitor WPBR, at least in the short-term. <br> Whitebark pine will likely be a species needing directed conservation attention in Idaho and elsewhere for many years. Its wildlife, water yield, aesthetic, and other high elevation ecosystem values cannot be readily replicated. The monitoring program provides information relevant to understanding the health and quantifying threats to whitebark pine on the Sawtooth NRA. This information benefits efforts aimed at ensuring the long-term conservation of whitebark pine and its forest ecosystem values.

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Reference Code: U14MAN02IDUS <br>

Full Citation: Monitoring white pine blister rust in whitebark pine communities on the Sawtooth National Recreation Area, Idaho <br>

Location: ELECTRONIC FILE - BOTANY: PLANT SPECIES: {Pinus albicaulis} <br>

Keywords: whitebark pine, Pinus albicaulis, mountain pine beetle, Dendroctonus ponderosae, white pine blister rust, Cronartium ribicola, Sawtooth National Forest <br>