Lecanoromycetes

Lecanoromycetes represents the largest class of fungi, most of which are lichenized. In an agricultural context, they are not typically classified as true plant pathogens or diseases that infect living tissues. Instead, they act as epiphytes—organisms that grow on the surface of plants, primarily utilizing the bark of trees as a physical substrate rather than as a nutrient source.

The presence of these organisms is often a biological indicator of the plant's physiological state. While they do not directly invade the vascular system or cause lesions, they frequently colonize trees that are already weak, neglected, or aging. Their existence on a tree canopy is a symptom of environmental factors rather than a primary infection, appearing more readily on trees with compromised growth rates.

Various crops, particularly fruit trees like apple, pear, and plum, are prone to hosting these lichens. They thrive in environments characterized by high humidity, limited sunlight, and poor air circulation within the canopy. These conditions are commonly found in older, overgrown orchards where regular pruning and management have been neglected for several years.

The indirect harm caused by Lecanoromycetes is associated with the ecosystem they create on the tree bark. The dense, sponge-like structure of lichens traps moisture, which may cause bark rot, and serves as an ideal overwintering habitat for harmful insects such as scales and mites. By harboring these pests, they indirectly facilitate the spread of genuine diseases and insect infestations within the orchard.

Management and preventative strategies focus on improving the overall health and vigor of the tree. Recommended practices include:

• proper pruning to increase light and airflow throughout the canopy;
• mechanical cleaning of bark surfaces to remove excess growth;
• applying whitewash or copper-based fungicides to inhibit colonization;
• optimizing fertilization and watering schedules to ensure strong tree growth.