Parmeliaceae lichens

It is important to clarify that Parmeliaceae are a family of lichens, not a disease in the botanical sense (like fungal pathogens). However, in orchard management, their presence is often categorized as a symptom of tree neglect or decline. They function as epiphytes that utilize the tree surface as a substrate for growth.

While they do not directly extract nutrients from the host plant, their presence is problematic for tree health. By covering the bark, these lichens physically obstruct lenticels, which are essential for gas exchange. This restriction forces the tree to function under hypoxic conditions, leading to poor vitality and reduced yields.

Fruit-bearing species, particularly apples, pears, and plums, are the most frequent hosts. Conditions favoring their colonization include high humidity, poor air circulation within the canopy, and mature trees with aging, fissured bark that provides an ideal anchor point for lichen spores.

The signs of lichen colonization are distinctive: leaf-like or shrubby growths ranging in color from pale gray to brownish-green. Beyond the aesthetic impact, these mats provide shelter for overwintering pests such as scale insects, mites, and various fungal spores that can later trigger infectious diseases.

• Implementing regular pruning to ensure proper aeration and sunlight penetration within the canopy.
• Manual removal of lichens using soft wire brushes when the bark is damp.
• Applying horticultural lime or copper-based sprays to sanitize the trunks.
• Improving overall soil fertility to promote faster bark growth and natural shedding.
• Conducting routine winter sanitation to remove dead wood and lichen-covered branches.