Red ring rot

Red ring rot, caused by the fungus Phellinus pini, is a severe wood decay disease that significantly impacts forest health by inducing heart rot in mature conifers. This pathogen is a perennial bracket fungus belonging to the Basidiomycetes class, known for its ability to digest wood components like lignin and cellulose.

The fungus affects a variety of conifer species, with the most notable hosts being pines, spruces, larches, and Douglas Fir. Infection typically initiates at the site of branch stubs or stem wounds, where fungal spores germinate and establish the mycelium that eventually colonizes the heartwood of the host tree.

Key symptoms include the emergence of woody, hoof-shaped conks on the bark of the host tree, usually near branch stubs. Internally, the wood undergoes a transformation, developing a distinct reddish-brown color followed by the formation of white, mycelial-filled pockets, which gives the wood a characteristic ringed pattern when cross-sectioned.

The development of Phellinus pini is highly dependent on the age and condition of the forest stands. Mature forests are particularly susceptible due to the accumulation of wounds and branch stubs over decades. High humidity and cool temperatures facilitate the production and dispersal of spores, which move through the air to colonize new entry points in the stand.

The impact of this disease on forest economics is significant, as it degrades timber quality and causes substantial volume loss. Furthermore, it predisposes trees to stem breakage and windthrow. Management relies heavily on cultural practices, such as selecting resistant species, minimizing mechanical damage during harvest, and conducting regular sanitation cuts to remove heavily infested trees before spores can spread.

• Early identification of conks on tree trunks.
• Removal of infected trees to lower spore load.
• Careful harvesting to avoid damaging remaining trees.
• Forest rotation management to reduce susceptibility.