British Columbia's Southern Interior Forests Armillaria Root Disease Stand Establishment Decision Aid

Abstract

In the Southern Interior of British Columbia, Armillaria (Armillaria ostoyae) root disease (DRA) causes considerable losses in immature stands by killing natural and planted coniferous trees. Tree mortality usually begins about 5–7 years after stand establishment, peaks around age 12, and then declines, although mortality can continue throughout a rotation. On the roots of older trees, repeated non-lethal infections will result in growth loss. The disease also increases the susceptibility of trees to attack by other pathogens and insects. DRA poses a long-term threat to forest productivity and sustainable forest management because current silviculture practices increase the amount and potential of Armillaria inoculum and put regenerated or residual trees at risk of becoming infected. This threat can be moderated by planting trees that are more resistant to Armillaria or by modifying silviculture practices to minimize exposure of trees to Armillaria inoculum in managed, secondgrowth stands. This extension note provides a revised table of host susceptibility ratings for species as well as a decision key to help natural resource managers choose from among several different treatments.