Peltigeraceae lichens

The Peltigeraceae family comprises various species of foliose lichens often found on tree bark. While commonly mistaken for a disease, they are biologically defined as epiphytes. These organisms use the tree bark merely as a substrate for growth and do not extract nutrients from the plant, meaning they do not behave as direct pathogens or parasites.

These lichens predominantly inhabit mature or declining trees, as well as plants in poorly maintained orchards. They thrive in environments where bark growth is slow or has ceased, allowing the lichen thallus to establish a firm attachment. On vigorous, rapidly growing young trees, you will rarely see significant colonization of Peltigeraceae.

The visible symptoms of their presence include large, flat, leaf-like lobes that cling tightly to the bark surface. The color range is usually shades of gray, green, or brown. If these lichens are proliferating on your trees, it is an indirect indicator of tree stress, age, or poor canopy aeration rather than a primary infection that requires fungicides.

Environmental conditions favoring the spread of Peltigeraceae include high humidity, lack of sunlight, and limited airflow through the tree canopy. These conditions are typical in unpruned, dense orchards where moisture persists on the branches for extended periods, facilitating the germination and growth of lichen spores.

While the lichen itself is harmless to tree sap, it can pose an indirect risk by providing shelter for overwintering pests, such as scales or mites, which may then infest the tree. To manage their spread, focus on cultural practices such as regular crown thinning and sanitary pruning. Mechanical removal using soft wire brushes, followed by applications of copper-based treatments, can help maintain clean bark and plant health.