Diploschistes scruposus

It is important to clarify that Diploschistes scruposus is not a plant disease. It is a species of crustose lichen that thrives as an epiphyte on rocks or, occasionally, on the bark of mature trees. It does not possess pathogenic properties and does not derive nutrients from the plant host, meaning it poses no biological threat to crops.

As a biological entity, it represents a symbiotic association between a fungus and an alga. The lichen relies on the bark solely for structural support. It does not infiltrate living tissues or disrupt the physiological processes of the tree, such as photosynthesis or nutrient transportation.

The visual signs of its presence include flat, gray or whitish thalli with small, sunken fruiting bodies known as apothecia. Since it is not a pathogen, it does not cause symptoms like necrosis, wilting, or lesions. If a tree shows signs of decline, it is almost certainly due to environmental stressors or true fungal diseases, not the presence of this lichen.

Development and spread of the lichen are favored by high humidity, moderate light, and a stable, undisturbed surface. Because it prefers stable substrates, it is significantly less common in commercial orchards where intensive pruning, chemical treatments, and orchard sanitation are standard practices.

No protective or chemical measures are required to combat this species, as it is harmless to plant health. If the appearance of lichen is undesirable for aesthetic reasons, standard maintenance practices such as thinning the canopy to increase airflow, cleaning the bark during dormancy, and maintaining general tree vigor are sufficient to discourage its colonization.