Peltigera

It is important to clarify that Peltigera is a genus of large foliose lichens, not a plant disease in the pathological sense. In agronomic practice, their appearance on tree bark or soil is primarily used as a bioindicator, suggesting that a tree may be experiencing physiological stress, reduced growth vigor, or that the orchard environment is overly humid and poorly ventilated.

Biologically, Peltigera is a symbiotic organism comprising fungi and cyanobacteria or algae. They do not consume plant sap and are not true parasites. However, their physical presence on a tree trunk can indicate that the bark is aging or necrotic, providing a perfect foundation for these epiphytes to colonize and spread across the tree's surface.

Symptoms of their presence include the development of large, leathery, lobed thalli that range in color from brownish-gray to green. While they do not directly cause tissue necrosis, they can create micro-habitats that harbor various insect pests, such as scale insects or aphids, which find shelter underneath the lichen cover, potentially leading to secondary infestations.

The conditions favorable for the development of Peltigera involve high humidity, poor air circulation, and low light exposure within the canopy. Neglected orchards with dense, unpruned trees are the most susceptible to colonization, as the stagnant microclimate prevents the bark from drying out sufficiently after rainfall.

Management and preventative strategies focus on enhancing overall tree health. Regular sanitary pruning is essential to improve airflow and sunlight penetration. Additionally, mechanical cleaning of the bark, followed by professional whitewashing with lime-based solutions, is highly effective. In severe cases, copper-based fungicides can be applied to suppress lichen growth and sanitize the tree surface.