Byssoloma marginatum

Byssoloma marginatum is a species of lichen belonging to the Pilocarpaceae family. Often confused with plant pathogens due to its presence on the surface of leaves, it is scientifically classified as a foliicolous lichen, which lives as an epiphyte on the foliage of evergreen plants.

The organism consists of a symbiotic relationship between a fungus and an alga. Unlike parasitic diseases, it does not penetrate the vascular system of the host plant or extract nutrients directly from the living tissue. It primarily uses the leaf surface as a stable substrate to colonize and grow, typically in tropical or subtropical environments.

The host range for this species includes a variety of broad-leaved evergreen trees and ornamental shrubs. In greenhouses, it becomes a point of interest when management practices, such as excessive misting or poor air circulation, create a microclimate that supports lichen growth on the foliage.

Symptoms are identified by thin, crust-like spots with well-defined margins, typically green to grey in color. Because it is an epiphyte, the leaf tissue underneath the lichen remains healthy and intact. However, heavy colonization can potentially interfere with the plant’s photosynthesis by obstructing light exposure.

Management of Byssoloma marginatum is primarily based on environmental control rather than chemical intervention. To prevent its spread, greenhouse managers should improve air circulation, reduce relative humidity, and ensure adequate spacing between plants. As it is not a pathogenic fungus, the application of fungicides is generally unnecessary and ineffective.