Stumping to Reduce Impacts of Tomentosus Root Disease: 28 Years Later, Was It Worth the Effort?

ABSTRACT Stump removal has been used to control impacts from other root diseases but to the best of our knowledge our study is the first to report long‐term results of stumping to control Tomentosus root disease. Tomentosus root disease ( Onnia tomentosa ) causes root and butt rot and is the dominant pathogen of interior spruce ( Picea engelmanni × Picea glauca ) in central British Columbia, Canada. We went to considerable effort to quantify the incidence and distribution of infected stumps from the prior stand and to account for it in our study design. Despite this, we found a poor relationship between both the basal area of pitted decay and the number of infected stumps and the incidence of disease in planted spruce. After 27 growing seasons, we found trees that had become infected with O. tomentosa by Age 22 grew significantly less (1.7 m) than uninfected trees. We found trees planted in stumped plots grew significantly larger in both height and diameter for several years but were no larger than trees in the control by the 27th growing season. Most importantly, after 28 years, we found the stumping treatment failed to significantly reduce the incidence of infection and mortality in planted spruce trees.