Heart rot

Heart rot is a fungal disease affecting the central, innermost wood of living trees. It is caused by various species of wood-decay fungi that enter the tree through wounds in the bark, such as broken branches, animal damage, or improper pruning cuts. These fungi decompose the lignin and cellulose within the heartwood, leading to structural weakening of the tree.

Heart rot is distinct from sapwood decay, which affects the outer, living layers of wood. Because heartwood is typically dead tissue, the tree can often survive for extended periods even with extensive heart rot, as long as the structural integrity is not severely compromised and the outer layers remain healthy and capable of transporting water and nutrients.

Symptoms of heart rot can be difficult to detect externally, especially in the early stages. Visible indicators may include:

• Fungal fruiting bodies (mushrooms or conks) growing on the trunk or branches. These are a definitive sign that decay is present within the tree.
• Hollow sounds when the trunk is tapped. This suggests significant internal decay has occurred.
• Cavities or open wounds in the trunk or branches, indicating points of entry for the fungi.
• Unexplained branch dieback or overall decline in tree vigor.
• Bulges or swelling on the trunk, potentially indicating internal decay and a reaction by the tree to compartmentalize the damage.

The fungi responsible for heart rot vary depending on the tree species and geographic location. Common culprits include species of Fomes, Ganoderma, Phellinus, and Trametes.

Management of heart rot is primarily preventative. Proper pruning techniques, protection of the bark from damage, and maintaining tree health can reduce the risk of infection. Once heart rot is established, there is no cure. Management focuses on assessing the tree's structural stability and, if necessary, removing hazardous trees to prevent property damage or injury. Cabling and bracing may be used in some cases to provide temporary support to weakened trees.