Not sure where to put this, but would love some feedback.
I first selected and cut out the lichen, and copied it to make it bigger. I took the colour from the lichen and made a solid colour layer below with that colour. Then I superimposed a damaged gumleaf over the lot. The lichens and gumleaf were set to luminosity and I fiddled with the opacity to get the effect I wanted.
I never cease to be amazed by the different patterns achieved by insects eating leaves.