Catillaria

Catillaria is a genus of lichen-forming fungi often found on the bark of various trees. While not always directly parasitic, these organisms form dense colonies on the bark surface, which can negatively influence the host tree's physiological functions by reducing gas exchange through the bark pores.

The causative agent belongs to the Catillariaceae family. These organisms are highly resilient and thrive in environments with high humidity and limited airflow. Their presence indicates that the tree's bark surface remains damp for long periods, which is a common issue in poorly maintained or overgrown orchards.

This condition primarily affects fruit-bearing trees such as apples, pears, and plums. Older trees with rough, textured bark are more susceptible to colonization. When these lichens cover extensive surface areas, they create a shelter for various insects and pathogens, potentially exacerbating other diseases like cankers or fungal blights.

Symptoms include the appearance of colorful crusts or patches on the trunk and limbs. In advanced stages, these patches can obscure the bark condition, making it difficult for growers to notice early signs of mechanical damage or rot underneath the lichen layer, leading to long-term structural weakness.

• Improve air circulation through regular pruning.
• Mechanical removal of lichen using soft brushes or scrapers.
• Application of specialized iron sulfate treatments.
• Routine white-washing of trunks in autumn and spring.
• Monitoring orchard humidity and drainage levels.

Effective management focuses on creating a healthy, well-ventilated orchard environment. Regular maintenance, including the removal of dead wood and proper crown management, prevents the excessive growth of Catillaria and ensures the longevity and productivity of the trees by keeping the bark surface clean and healthy.