Lichinales

The order Lichinales consists of unique ascomycete fungi that form symbiotic relationships with cyanobacteria. From an agronomic perspective, they are classified as lichenized epiphytes. While they do not act as direct plant pathogens that kill living tissue, their massive development on the bark of fruit trees often signals an aging or neglected orchard environment.

Common hosts for Lichinales include mature fruit species like apples, pears, and stone fruits. These organisms settle primarily on the bark of trunks and older branches, finding the necessary substrate and micro-moisture in the deep fissures of the bark to sustain their growth and reproductive cycles.

Symptoms of their presence include the appearance of distinct, often dark or scaly thalli growing on the tree surface. Since they are epiphytic rather than parasitic, they do not infiltrate the tree's vascular system. However, they compete for surface space and moisture, and their presence is a clear indicator of poor airflow and high ambient humidity around the tree.

Development and spread of Lichinales are significantly enhanced by environmental factors such as high atmospheric humidity, shade from dense canopies, and poor circulation. These conditions allow the spores and fragments of the thalli to establish themselves easily on new surfaces, leading to rapid colonisation of the orchard.

The economic impact of Lichinales is primarily indirect. They create a protective habitat for overwintering pests, such as scale insects and mites, and can harbor fungal spores of various diseases. Furthermore, heavy covering of the bark can interfere with normal gas exchange, potentially reducing the tree's overall vigor over time.

Effective prevention and control measures include:

• Systematic canopy thinning to increase airflow and sunlight penetration.
• Mechanical cleaning of bark using non-damaging tools during the dormant period.
• Application of white-wash containing copper-based fungicides to the trunks.
• Maintaining balanced soil moisture to regulate the orchard's microclimate.