Yield reduction in spruce infected with Armillaria solidipes in the southern interior of British Columbia

The effect of non-lethal root infection on the yield of planted spruce (Picea engelmannii x glauca hybrid spruce) in southern British Columbia was determined in a 34-year-old, mixed-species stand infected with Armillaria solidipes Peck. Yield reduction correlated with trees' infection duration. Individual trees infected for 24 years had about 42% less volume than their healthy equivalents. Using the incidence of infection in stands in this area and the individual losses per tree, reduction at the stand level was approximated at 11% and increasing.