A first assessment of the biocidal efficacy of plant essential oils against lichens on stone cultural heritage, and the importance of evaluating suitable application protocols

•A plant essential oils (EOs)-based product effectively devitalized saxicolous lichens.•Its effect was assessed both in semi-arid (Iran) and temperate (Italy) heritage sites.•Its biocidal efficacy was similar or even higher than that of traditional biocides.•A partial persistence of viability was shown by some species of the semi-arid site.•The application protocol was crucial to make the EOs treatment effective.