Recolonization dynamics of lichens after biocidal treatments: A limitation in the spreading of water-based solutions beneath thalli as species-specific influencing factor

Lichen recolonization on heritage surfaces, particularly for species with low propagule dispersal potential, begins immediately after biocidal treatments, challenging the assumption that these interventions fully devitalize lichens. Research on marble balustrades from two UNESCO World Heritage Sites in Italy revealed that water-based biocides may not penetrate deeply enough beneath lichen thalli to affect their hyphal structures, leaving viable remnants that rapidly restart recolonization. This finding suggests a species-specific resilience linked to the depth of hyphal penetration and substrate properties, which could explain the frequent recurrence of Megasporaceae and Verrucariaceae on recently cleaned surfaces. The study used marble blocks to simulate biocide spread, confirming that lichen cover influences water absorption but does not prevent some hydrophobic volumes beneath thalli from acting as refuges for lichen survival.

Cicardi, M., Matteucci, E., Rao-Torres, G., Canepa, M. C., Castelli, D., Ferrando, S., Antonietti, S., Piqué, F., & Favero-Longo, S. E. (2025). Recolonization dynamics of lichens after biocidal treatments: A limitation in the spreading of water-based solutions beneath thalli as species-specific influencing factor. Journal of Cultural Heritage, 73, 454–464. https://doi.org/10.1016/j.culher.2025.04.005