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Cronartium ribicola, the introduced pathogen that causes white pine blister rust ( WPBR), continues to spread to additional limber pine populations in the Southern Rocky Mountains of Colorado and Wyoming. Because WPBR can severely impact ecosystems, forecasts of its potential distribution and incidence would be useful to land managers. Site and climate data from long infested study areas in Wyoming were fit with two regression models [logistic and classification and regression trees ( CART)] to determine the environmental conditions associated with the distribution of WPBR. These models were then used to map limber pine stands at risk of infestation by C. ribicola throughout Wyoming (where it has long occurred) and Colorado (where it is just becoming established). Although variables representing vegetation and landform could identify infested plots, 1-km-scale climate variables for monthly temperature and moisture were better predictors of current WPBR distribution and were available for mapping expected future distribution across the region. Of 280 485 ha where limber pine was projected to occur in Colorado, 41% was forecast by the logistic model to be at risk of infestation, and 53%, by the CART model. Of an estimated 782 229 ha in Wyoming with limber pine, the logistic model projected 61% to be at risk; CART projected 79%. Additional regression models were fit with site and climate data to predict WPBR incidence (per cent of trees infected) and intensification (incidence/age of the oldest canker). Nearly one half of the plot-to-plot variation in incidence was explained using environmental variables readily available to land managers. Although mean plot incidence increased over time, mean intensification decreased 50% per decade. This work provides managers with several tools to reduce uncertainty over the expected distribution and incidence of WPBR, but surveillance and monitoring remain prudent activities for supplementing forecasts of WPBR epidemics. [ABSTRACT FROM AUTHOR]

Ponderosa pine ( Pinus ponderosa) in the Black Hills National Forest, SD, USA, was surveyed for Armillaria root disease (ARD). The root pathogen Armillaria ostoyae occurred on ponderosa pine seedlings, saplings, pole-size trees and large-diameter trees. The mean incidence of aboveground disease symptoms by stem count was low (0.2%), but in certain areas, the incidence was higher, affecting the regeneration success and tree longevity. Symptomatic ponderosa pine were in areas characterized by having higher elevation, greater annual precipitation, more seedlings, bigger large-diameter trees and greater odds of past harvesting activity than in areas without root disease. Stump density was positively spatially correlated with root disease incidence. No particular soil type was related to disease occurrence; though, in areas with symptomatic trees, soil available water holding capacity (AWC) was greater and soil permeability was less where root disease was present. Spatial analysis confirmed the relationships found in linear correlations, with soil AWC and stump density positively and soil permeability negatively correlated with per cent infected stems ha−1 and basal area infected. [ABSTRACT FROM AUTHOR]

The article presents a study on the impact of firewood transport by state and national park campers on the movement of exotic or native tree pests. The researchers surveyed campers in different campgrounds in various Colorado State Parks in 2008, which were stratified to cover the areas west of Front Range, the mid-state Front Range areas and the eastern plains. They suggested that campgrounds and parks should promote the sale of local wood to incoming visitors before their arrival and should ban all firewood that is not locally produced or treated.