Effect of Armillaria root disease on quality and value of green Douglas-fir lumber

Abstract

For a few tree species, scattered accounts of impact caused by root disease exist in the literature mainly at the tree level. No product quality impacts have ever been measured or properly costed. To provide some information on value impacts, green rough-sawn Douglas-fir lumber was cut from trees with and without Armillaria root disease. This produced 80 boards from six trees in two planted stands. Fewer boards came from living diseased trees compared to healthy trees of similar diameter (1.3 m) at both sites, suggesting that disease may affect stem taper or form. Lumber from diseased trees was affected most often by warp and for healthy trees by knots, but warp affected value the most. Disease appears to have at best no effect, and at worst, a negative effect on lumber value but is not likely to increase value. This is the first report of the impact of a root disease on lumber quality and value, but further work would be required to properly assess this.Key words: disease, Armillaria root disease, conifer, Douglas-fir, wood quality, lumber warping, lumber value, lumber grading 1 Natural Resources Canada, Canadian Forest Service, Canadian Wood Fibre Centre, 506 West Burnside Rd., Victoria, British Columbia V8Z 1M5. E-mail: mcruicks@nrcan.gc.ca of chronic infection on the quantity, quality, and value of timber products has rarely been considered. The objective of the study was to determine how a root disease may affect the endproduct quality of plantation-grown trees, using three different Canadian grading standards and a US pricing system that reflects where most of the lumber is sold. If non-lethal disease affects lumber quality through heterogeneous radial growth and increased distortion, then the disease impacts in hosts will perhaps be more complex than a simple volume reduction caused by reduced tree vigour.Armillaria ostoyae (Romagn.) Herink, the fungus mainly causing Armillaria root disease in Canada occurs widely in the northern hemisphere. Over 30 other species of this fungus extend the range of the genus to the global scale. Apart from causing mortality and affecting diameter and height growth (Cruickshank et al. 2009), little is known about the level of disease impact at the stand level in Canada despite the wide distribution and occurrence. The fungus also infects all tree species making it difficult to manage. More is known Douglas-fir (Pseudotsuga menziesii var. glauca [Beissn.] Franco) is used mainly for structural purposes because the wood is moderately hard and very strong, but it is also used for interior and exterior finishing and pulp. Conversion into high quality forest products has been considered with respect to site index, stand density, fertilization, and pruning (Kellogg 1989). Other work showed that pests in young stands are not well recognized in silviculture surveys, and the silvicultural prescriptions often do not take into account the impact of pests, especially of diseases (Humphreys and Van Sickle 1992). Pests principally draw attention when they cause short-term mortalit...

Site, plot, and individual tree yield reduction of interior Douglas-fir associated with non-lethal infection by Armillaria root disease in southern British Columbia

“…As long as the infected trees live, yield reduction will be a limiting stand factor; however, it is expected that mortality losses will increase in the planted stands with time. Also, if root disease negatively affects stem taper as it does with butt rot (Kallio and Tamminen, 1974), and wood recovery or timber product value are also affected (Cruickshank, 2010), then these need to be added to the impacts discussed here. Finally, root disease affects root biomass proportionally to stem biomass (Bloomberg and Hall, 1986), which together could affect carbon sequestration.…”

Allometries of coarse tree, stem, and crown measures in Douglas-fir are altered by Armillaria root disease

“…Stem form and size, somewhat related to height and diameter, are also important in Douglasfir because they affect value of high-quality saw logs (Kellogg 1989). Disease-caused alterations in annual ring and height growth might also affect value of wood products (Cruickshank 2010). Allometry is also used in models simulating tree growth for inventory which might better approxi- Fig.…”

Resistance and tolerance in juvenile interior Douglas‐fir trees Pseudotsuga menziesii var. glauca artificially inoculated with Armillaria ostoyae

“…Lack of timber product uniformity is one of the greatest problems faced by wood-use industries (Bowyer et al 2007), and wood quality, product recovery and piece size, all related to growth, are important determinants of Douglas-fir product value. Uniformity of ring width within stems and rings is strongly disrupted by root disease in the bottom several metres of the tree (Cruickshank 2002), lowering timber product value through piece size and ring heterogeneity (Cruickshank 2010) and possibly through increased stem taper (Cruickshank and Filipescu 2012). Disease tolerance might reduce this heterogeneity.…”