Laminated Root Rot - Disease Cycle and Transmission

Disease Cycle and Transmission

There are two types of the Phellinus; one that causes laminated root rot in Douglas fir, Grand fir, and Hemlocks and the other that causes butt rot in Western red cedar. The mycelium of this fungus doesn’t grow in the soil and also its spores are not spread by wind like most fungal pathogens. Infection occurs when roots of healthy trees grow in contact with infected roots. After initial contact with a living root, the mycelium grows on the bark, extending only a few millimeters into the surrounding soil. The mycelium penetrates the host through injured bark and advances proximally and distally along newly infected roots. It eventually penetrates through the host’s cambium and grows inside the wood causing decay and death of living cells in the heartwood and sapwood. During this process of entering into the cambium, the pathogen kills the phloem and initiates the decay of the xylem. The pathogen utilizes both cellulose and lignin, weakening the plant and eventually this leads to its death Phellinus Weirii over-winters within infected stumps and can remain viable for up to 50 years It is also known to infect bark, but this infection process is not well understood. Older trees are more resilient to infection, although trees of all ages may be infected.