Post-spacing mortality of lodgepole pine from armillaria root disease

Abstract

To evaluate the threat of armillaria root disease in precommercially thinned lodgepole pine (Pinus contorta var. latifolia), a total of 66 15 × 15-m plots were established in dense lodgepole pine regeneration, 18 to 21 years after harvest, on three infested sites near Hinton, Alberta. Three treatments (2.5-m spacing, 1.5-m spacing and an unspaced control) were randomly applied to plots having similar densities and levels of mortality. After 11 years there was no significant difference among the treatments in cumulative percent mortality. Based on observed levels of mortality, it would appear that spacing need not be avoided in infested stands, although it likely would be prudent to space more closely than 2.5 m in younger stands and in parts of stands having more than 5–10% mortality. Key words: precommercial thinning, spacing, armillaria root disease, Armillaria ostoyae