Not about Orchids but is there a way to stop rot on a leaf?

[Roberta]

I don't grow this particular plant... but in general, the function of a leaf is to use photosynthesis to provide the energy that a plant needs to live (food) Roots take up water, leaves utilize that water plus CO2 from the air, to produce sugars - the chlorophyll in the green leaf is an energy factory. So it's the combination of leaves and roots that permits a plant to live. I'd leave the leaf alone. It looks like it is aging... the plant will drop it when it is no longer useful. When you're trying to get the plant established is not a time to be particularly concerned with aesthetics - it needs every bit that it has.