A method for estimating white pine blister rust canker age on limber pine in the central Rocky Mountains

Abstract

Epidemiological studies of white pine blister rust on limber pine require a temporal component to explain variations in incidence of infection and mortality. Unfortunately, it is not known how long the pathogen has been present at various sites in the central Rocky Mountains of North America. Canker age, computed from canker length and average expansion rate, can be used to estimate infestation origin and infection frequency. To investigate relationships between canker lengths and canker ages for limber pine, we collected live white pine blister rust branch and stem cankers from three locations in Wyoming and two locations in Colorado. We quantified relationships between various measures of canker length and an estimate of canker age based on dendrochronological analysis. Total branch canker length was strongly, negatively correlated (r = )0.79) with the first year of incomplete, annual ring formation (canker age). Mean longitudinal canker expansion rate was 8.4 cm year )1 for branch and stem cankers where branches distal to the canker were either dead or alive. Annual longitudinal canker expansion, however, was significantly greater on a stem or branch where the portion distal to the canker was alive (11.5 cm year )1 ) rather than dead (7.1 cm year )1 ). For branches or stems, proximal expansion rate (i.e., toward or down stem) averaged 4.9 cm year )1 . The circumferential canker expansion rate (around branch or stem) was greater for stem cankers (8.3 cm year )1 ) than for branch cankers (6.2 cm year )1 ). Additional site and host tree covariates did not improve prediction of canker age. Two simple linear equations were developed to estimate a canker age from total length of a canker with the distal portion either alive or dead. An appropriate sample of canker ages can be used to determine how long a limber pine stand has been infested with white pine blister rust and how frequently infections have occurred.

Ecology of whitebark pine populations in relation to white pine blister rust infection in subalpine forests of the Lake Tahoe Basin, USA: Implications for restoration

“…These authors also assume mycelium growth rate in branches to be 8 cm year À1 (Ettl and Cottone, 2002). However, the rate at which rust mycelium grows is mediated by environmental conditions in which hosts are growing (Buchanan, 1938;Kearns et al, 2009). We found relationships between soil properties and severity of stem girdling by C. ribicola.…”

Pruning Limber Pine to Reduce Impacts from White Pine Blister Rust in the Southern Rocky Mountains

“…length classes (e.g., 5, 10, 15, 20, and 25 in. long), that is a good indicator that infections are occurring most years (Kearns et al 2008). …”

“…(12 cm). Each bin represented approximately 1 year's linear expansion of cankers on live branches (Kearns et al 2008).…”

“…[4.2 cm]); thus, branches were easily cut with hand saws. Branch canker distance from the stem was different among 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00 99 Mosca Pass 2005 138 232 174 77 26 7 0 2010 89 102 56 28 17 2015 36 23 5 9 0 Vedauwoo Campground 2006 75 148 227 213 131 28 32 2 2011 8 44 39 27 7 2015 6 51 66 63 26 Canker length was used as a surrogate for how long a canker has been growing on a live branch based on previous research (Kearns et al 2008). 1 Canker counts in 2010/2011 and 2015 assessments included only cankers that became visually apparent since the previous assessment.…”

“…Thus, we collected the length of cankers that were assumed to have become visually apparent after the previous assessment (less than 25 in. [0.635 m] long in 2010 or 2011 or 2015) (Kearns et al 2008). Infected branches were assumed to be live if they had live cambium and live needles either proximal or distal to the canker.…”