Incidence of White Pine Blister Rust in a High-Hazard Region of Wisconsin

Abstract

Abstract The incidence of white pine blister rust, caused by the fungus Cronartium ribicola, was recorded in 61 pole and small sawtimber stands in northern Wisconsin where the risk of infection has long been considered high. A minimum of three, randomly located, 10 basal area factor prism plots were established in each stand. Topographic position, aspect, slope, tree density, habitat type, and the presence or absence of bole cankers were recorded at each plot. The mean incidence of infection was 7.2% for all study sites and 5.9% excluding data from Bayfield Peninsula. Mean incidence of cankered trees at this site was 15.9%. The following site factors were significantly correlated with increased incidence of blister rust: increased latitude, higher topographic position, northern aspect, lower total tree density, and absence of a hardwood overstory. Incidence was almost three times higher on ridge tops and shoulders (12.3%) than on flat or bottomland (4.7%). Habitat type was correlated with disease incidence only at the Bayfield Peninsula site, and slope was not significantly correlated with rust levels on any of the plots. North. J. Appl. For. 18(3):81–86.