Loxosporaceae lichens

The Loxosporaceae family represents a group of fungi characterized by a lichenized lifestyle within the order Lecanorales. In agricultural practice, they are identified as epiphytes that colonize the bark of fruit and forest trees. Unlike true plant pathogens, they do not infiltrate the vascular system of the host plant but rely on the bark solely as a stable substrate.

The biological nature of Loxosporaceae involves a symbiotic relationship between a fungal partner and algal cells. While they do not act as nutrient-stealing parasites, their presence is often misinterpreted as a primary disease. In reality, their settlement on bark is usually a sign of an aging or poorly ventilated tree canopy where the growth rate of the bark is insufficient to shed the lichen thallus.

Symptoms of infestation are characterized by the appearance of crustose or squamulose thalli on the tree trunks and main branches. These structures can vary in color and texture. If left unchecked, these colonies can cover large areas of the bark, particularly in humid or shaded environments, potentially obstructing the natural lenticel gas exchange process.

Environmental conditions conducive to their growth include high humidity, stagnant air, and lack of regular tree maintenance. Orchards with overly dense canopies that prevent sunlight penetration and air movement are particularly susceptible to widespread lichen colonization. They flourish in stable environments where there is minimal disturbance to the tree's surface.

The economic impact of Loxosporaceae is mainly indirect. The accumulation of lichens provides a refuge for various overwintering pests, such as mites and scale insects, and can create a moisture-retaining microclimate that promotes secondary fungal infections. Effective protection and management strategies include:

• Conducting regular crown thinning to improve air circulation.
• Mechanical removal of lichens using appropriate specialized brushes or scrapers.
• Applying lime-based whitewash to tree trunks as a sanitation measure.
• Monitoring tree vigor to ensure healthy bark shedding and growth rates.