Crepidotus applanatus

Crepidotus applanatus, commonly known as the flat oysterling, is a saprotrophic fungus that primarily functions as a decomposer of dead or dying wood. Within an agricultural or forestry context, it acts as a secondary pathogen, colonizing stressed or wounded deciduous trees. The fungus initiates a process of white rot, effectively breaking down the cellulose and lignin components of the wood, which can lead to structural instability of the affected plant.

The host range for this fungus includes various deciduous species such as birch, beech, poplar, and maple. Trees that have experienced prior damage—due to frost, insect attacks, or poor pruning—are particularly susceptible. The fungus typically exploits these points of entry to establish its mycelium within the heartwood or sapwood of the tree.

Symptoms are identified by the presence of small, shelf-like, or sessile fruiting bodies that are fan-shaped and whitish-creamy in color. These fruiting structures are often found clustered on the trunk or bark. Beneath the site of colonization, the wood typically exhibits signs of decay, appearing bleached, light in color, and soft to the touch, indicating internal tissue breakdown.

Development and spread are strongly correlated with environmental conditions. High humidity levels, moderate temperatures, and abundant rainfall provide the necessary moisture for the spores to germinate. The fungus spreads via air-borne spores, which land on vulnerable exposed tissues, particularly during periods of prolonged wet weather, making orchards with poor air circulation more prone to infestation.

To effectively prevent and manage the spread of Crepidotus applanatus, implement the following measures:

• Maintain good tree hygiene by promptly removing dead or diseased wood.
• Apply protective wound sealants or fungicides to tree cuts and damaged bark to create a barrier against spores.
• Improve air circulation in the garden through regular pruning to reduce excessive humidity around trunks.
• Monitor trees for early signs of decay and treat wounds immediately to prevent deeper colonization of the wood.