Megalosporaceae

Megalosporaceae is a family of fungi that form symbiotic relationships known as lichens. In the context of agronomy, they are classified as epiphytes rather than infectious plant pathogens. While they do not consume host tissues directly like parasitic fungi, their presence on tree bark can lead to several physiological and management concerns for growers.

The organism primarily colonizes the bark of trees as a physical substrate. Being an epiphyte, it derives nutrients from atmospheric deposition rather than from the tree itself. However, widespread colonization can interfere with gas exchange (respiration) of the bark, which can indirectly impact the health of older trees, especially in humid and stagnant air conditions.

These lichens typically thrive on trees with thick, mature, or decaying bark. They are commonly observed in neglected orchards or woody landscapes where moisture retention is high. Apple, pear, and various ornamental tree species are among the primary hosts where these lichens establish their characteristic apothecia structures.

Symptoms of colonization include the appearance of disc-shaped structures (apothecia) on the bark surface, which vary in color and size. These structures are visible indicators of the ecological conditions of the garden. If the coverage is extensive, it is a sign that the tree canopy is likely too dense and the airflow is insufficient for rapid bark drying.

• Symptoms: formation of visible, disc-like fungal structures on the bark.
• Conditions: high humidity, shaded locations, and poor tree canopy management.
• Economic impact: provides niches for pest insects, reduces bark respiration, and indicates poor tree health.
• Control: mechanical scrubbing of the bark, proper pruning, and whitewashing tree trunks.

Effective management and prevention require a proactive approach to tree maintenance. Regular pruning is the primary cultural practice that improves air circulation and sunlight penetration, effectively drying the bark and making it less hospitable for lichen growth. Additionally, cleaning the bark and applying lime-based whitewash during the dormant season are highly effective methods for disrupting the habitat of these organisms.