Alder bracket

Alder bracket (Inonotus radiatus) is a species of wood-decay fungus known for causing white rot in various hardwood trees. As a parasitic pathogen, it systematically breaks down the structural components of the tree, significantly shortening its lifespan and increasing the risk of structural failure and windthrow in forest ecosystems.

The fungus primarily targets species such as alder (Alnus), birch (Betula), hazel, and occasionally willow. It gains entry into the host through wounds, broken branches, or areas where the bark has been damaged by external stressors. Once inside, the mycelium colonizes the heartwood, slowly spreading throughout the trunk and root system.

Visual symptoms of Inonotus radiatus infection are marked by the presence of perennial fruit bodies. These brackets are usually small, woody, and rusty-brown in color, often growing in clusters on the stems of affected trees. Internally, the wood undergoes a transformation: it loses its density, becomes bleached, and develops distinct black zones characteristic of advanced wood degradation.

Environmental conditions that favor the fungus include persistent high humidity and temperatures that support fungal respiration. It is particularly prevalent in moist riparian habitats or shaded woodland areas. The spores are primarily dispersed via air currents during the warmer months, allowing the fungus to colonize new hosts through even minor surface injuries.

Management and prevention of Alder bracket involve rigorous monitoring and silvicultural practices:

• systematic removal and disposal of infected timber to reduce spore load in the environment;
• avoiding mechanical injuries to the trunks during maintenance and logging;
• maintaining overall tree vigor to enhance natural resistance;
• applying protective dressings to large pruning wounds to prevent fungal spore germination.