Pannaria

Pannaria (genus Pannaria) represents a group of foliose lichens that often colonize the bark of trees and shrubs. While they are not pathogens that feed on the host plant, their presence is frequently observed in neglected orchards or areas with high humidity and poor air circulation.

From an agronomical perspective, Pannaria acts as an epiphyte, using the bark surface primarily for structural support. Although they do not directly extract nutrients, an extensive lichen cover can interfere with the bark's ability to "breathe" through its lenticels, potentially weakening the overall vigor of the tree.

These lichens primarily affect older fruit-bearing trees such as apples, pears, and stone fruits. They tend to proliferate in shaded, damp conditions where sunlight rarely reaches the lower branches and trunk, allowing the lichen to establish itself on the moist, stable surface of the bark.

Symptoms are identified by the appearance of brown or greyish scaly, leaf-like patches on the trunks and major limbs. If left unchecked, these structures grow quite dense, creating an ideal micro-habitat for overwintering pests, mites, and fungal spores that can damage the tree's vascular health.

Management strategies focus on physical and chemical control. Regular pruning to improve air circulation is the first step. For heavy infestations, removing loose, dead bark during dormant seasons and applying copper-based treatments or lime whitewashing of trunks are highly recommended to inhibit lichen regrowth.