Preliminary evidence under this study revealed that western red cedar shows greater resistance to invasion of host tissue by A. ostoyae. Examination of lesions resulting from natural infection and inoculation on roots showed a more rapid response to phellogen and cambial invasion compared to other common conifers. Resistant reactions involving necrophylactic periderm formation in the inner bark were frequent. A barrier zone formed by the uninjured cambium produce a large number of axial parenchyma that accumulated pigmented phenolics. The formation of these unique cells will limit the extent of cambial invasion by the fungus and compartmentalize the infection to woody tissue formed prior to injury. Also, an early initiation of vascular restoration in response to invasion by the fungus suggests that cedar may have a distinct advantage over other conifers with a more rapid response to wound healing. The majority of this work is ongoing and more work is needed to confirm the mechanisms of resistance in cedar against infection by A. ostoyae. However, our preliminary work has identified and characterized natural resistant mechanisms operating in western red cedar that appear to be effective at limiting the advance of the fungus. More extensive sampling for cedar is planned for the next fiscal year throughout the moist warm forests of the southern interior. Results will determine whether the inclusion of western red cedar among planted species will reduce the overall impact of Armillaria root disease to more tolerable levels.
Bart J. Van Der Kamp.
Forest Investment Account (FIA). 2004. Reducing the impact of Armillaria root disease via mixed species plantations including western redcedar. Forest Investment Account (FIA) - Forest Science Program. Forest Investment Account Report. FIA2004MR252