Candelariales fungi

The order Candelariales comprises a specific group of fungi, predominantly classified as lichenized fungi within the Lecanoromycetes class. In agricultural and horticultural settings, their role is often debated, but they are typically observed as surface colonizers that can impact the health of woody plants by obstructing bark respiration.

The causative agents are species such as those in the Candelariella genus. These organisms develop as crustose thalli, typically displaying vibrant yellow to greenish-gold colors. They attach firmly to the bark of trees, acting as epiphytes that, if left unmanaged, can become a structural nuisance on the host plant.

Fruit trees such as apple, pear, and plum are most commonly affected, especially in older, poorly maintained orchards. The main symptoms are the formation of dense, crust-like patches that spread over the bark surface. These colonies create a physical barrier that restricts the plant's ability to undergo gas exchange, eventually weakening the tree's overall vigor.

Environmental conditions play a critical role in their propagation. High relative humidity, persistent shade, and poor airflow within the orchard canopy are primary drivers. Without proper sunlight penetration, the bark remains damp for extended periods, allowing fungal spores to germinate and colonize the surface successfully.

Management strategies for control include:

• Regular pruning to improve air circulation and sunlight access to the trunks.
• Mechanical cleaning of affected bark areas using soft brushes.
• Applying copper-based fungicides to inhibit fungal growth during dormancy.
• Maintaining tree vigor through proper fertilization and irrigation to strengthen natural defenses.