White butt rot - White laminated rot
Damage, symptoms and biology
Ceriporiopsis rivulosa is recognized as the most important butt rot of mature western red cedar in the coastal regions of British Columbia. Since decay develops readily early in the life of the tree (when pole-sized), butt logs of mature trees often have significant levels of damage.
The decays caused by C. rivulosa and the cedar form of Phellinus weirii are very similar in gross appearance, particularly in early stages of decay. However, they can be distinguished when laminations form; C. rivulosa shows conspicuous, white mycelial flecks between the laminae, and the final stage of decay is crumbly. In contrast, Phellinus weirii develops dark brown setal hyphae between the laminations and the wood shows long striations of white cellulose-like material. These striations give the final decay a fibrous texture. In culture C. rivulosa produces clamp-connections whereas P. weirii does not.