Branched oyster mushroom

Branched oyster mushroom (Pleurotus cornucopiae) is a wood-decaying fungus that acts as a pathogen in horticultural settings, leading to white rot. While often harvested as a culinary mushroom, its presence on live trees indicates the degradation of wood tissues, which compromises the structural integrity of the host plant.

The fungus typically attacks deciduous trees such as elms, beeches, and oaks, but can also inhabit fruit trees like apples and pears. It primarily colonizes wood through entry points such as wounds, cracks in the bark, or pruning cuts that have not been properly sealed, allowing the mycelium to penetrate the internal woody layers.

Symptoms of infestation are marked by the appearance of funnel-shaped fruiting bodies, often clustered together on the trunk or exposed roots. Internally, the wood becomes bleached, spongy, and loses its mechanical strength, as the fungus secretes enzymes that break down lignin and cellulose, effectively hollowing out the tree from within.

The development and spread of Pleurotus cornucopiae are favored by high humidity and moderate temperatures. Spores are primarily wind-dispersed, finding suitable germination sites on vulnerable, injured bark surfaces. In neglected orchards, the presence of decaying stumps acts as a reservoir for spores, facilitating the infection of neighboring healthy trees.

The impact of this fungus is significant, as it leads to tree decline, reduced fruit yields, and eventual structural failure. Effective management and prevention strategies include the following:

• Rigorous sanitation, including the removal of dead or infected branches and their immediate destruction.
• Proper wound dressing for pruning cuts to prevent fungal colonization.
• Removal of old stumps or decaying logs that serve as inoculum sources within the garden.
• Promoting tree vigor through appropriate fertilization and water management to enhance natural defense mechanisms.