Stringy butt rot

Stringy butt rot is a destructive fungal disease caused by Perenniporia subacida, a white-rot pathogen that colonizes the roots and lower stems of various conifer species. The fungus degrades lignin and cellulose, leading to a loss of structural integrity in the tree's base, often resulting in significant timber loss in commercial forestry.

The disease primarily targets conifer trees, with Douglas Fir being one of the most susceptible species. The infection typically begins in the root system, where the fungus slowly progresses toward the root collar, eventually spreading into the heartwood of the lower trunk, causing the characteristic decay pattern associated with the disease.

Symptoms of the infection include a distinct bleaching of the wood, which takes on a stringy, fibrous texture as the degradation advances. In advanced stages, narrow dark lines, known as zone lines, may appear within the decaying wood, and the presence of leathery, perennial fungal conks at the base of the infected trees serves as a diagnostic indicator of the pathogen.

The development of stringy butt rot is favored by high moisture conditions and the presence of root wounds that provide entry points for the fungus. Spore dispersal plays a role in new site colonization, but the fungus primarily spreads through root contact, as the mycelium can bridge the gap between infected and healthy root systems in dense plantations.

The economic impact is primarily related to the loss of tree stability and timber degradation, which necessitates effective management practices.

• Implement site-specific sanitary thinning to remove infested stumps.
• Avoid machinery-induced root damage during silvicultural operations.
• Maintain proper tree spacing to minimize root grafting and underground infection spread.