Leproloma membranacea

Leproloma membranacea (often identified under the genus Lepraria) is a type of crustose lichen that forms on the bark of living trees and woody plants. While it is not a direct plant pathogen, it acts as an epiphyte that can significantly affect the surface health of the bark and indicate a decline in the host plant's vigor or environmental balance.

The organism appears as a thin, powdery, or granular crust, typically pale gray or whitish in color. It colonizes the bark by forming a symbiosis between a fungal partner and algae. As the colony matures, it spreads across the trunk and major branches, forming a cohesive layer that adheres tightly to the surface of the wood.

The development of this lichen is highly dependent on environmental conditions, specifically high humidity, lack of direct sunlight, and stagnant air movement. It thrives in neglected orchards or dense garden landscapes where the bark remains moist for extended periods, preventing the plant from performing necessary gas exchange through its natural pores.

The primary concern regarding this organism is its role as a shelter for various plant pests, including scale insects and mites, which hide beneath the lichen crust. Furthermore, by hindering the bark's ability to breathe and dry out, it creates a conducive environment for secondary wood-decay fungi and bacterial infections that can damage the tree's health.

Effective management focuses on preventive horticultural practices rather than chemical eradication. Mechanical removal using wire brushes or scrapers during the dormant season is the most direct solution. Following this, applying a lime-based whitewash with copper compounds helps to sanitize the bark and inhibit the re-establishment of lichen colonies, while proper pruning ensures better light and air penetration.