Cetraria

It is important to clarify that Cetraria is not a disease in the biological sense, but a genus of lichens. In agronomic practice, they are classified as epiphytes. They do not feed on plant tissues, but their presence is a clear indicator that a tree is aging or suffering from a lack of vigor and proper care.

The lichen is a symbiosis between a fungus and an alga. While it does not directly parasitize the plant, its dense growth on the bark creates a micro-habitat for many orchard pests and fungal pathogens. It restricts the gas exchange of the bark, which can lead to premature corking and weakening of the plant.

Cetraria most frequently colonizes fruit trees such as apples, pears, and plums, especially in older, poorly maintained orchards. High humidity and poor air circulation within the tree crown are the primary environmental drivers that allow these lichens to thrive on the bark surface.

The main signs of colonization are bushy or leafy, often brownish-colored thalli on the trunk and primary branches. While the lichen itself is slow-growing, ignoring it allows for the accumulation of moisture and organic debris, which provides a hiding place for overwintering pests and disease spores.

Effective management and protection strategies include:

• Regular pruning to improve light penetration and air circulation.
• Manual removal of lichens and dead bark using specialized scrapers during humid weather.
• Applying a 3-5% iron sulfate solution while trees are dormant to eliminate lichen spores.
• Whitewashing trunks with lime-based solutions for disinfection and protection.
• Implementing balanced nutrient management to improve the overall health and resistance of the orchard.