A few days back I realized there is some kind of fungus-like growth on my lemon tree and it has affected the plant growth so much. The leaves just don't grow and the tree seems to dry out. Today I noticed one more tree (I don't know the name of the tree) with a similar condition.
What kind of infection could this be and how can I save my trees?
It is lichen, yes - if it's only excessive on dead branches, that's why it's proliferating, because the wood is dead, although it does occur on live branches or trunks of trees as well, though not quite so enthusiastically.
It won't be the cause of the dieback on some branches, it's just opportunistically decided to grow there. You may wish to prune out dead wood from the tree/s.
It's lichen and is not a problem. It won't hurt your lemon tree.
From the leaflike bits, it looks like there is some liverwort, marchantia, on there too: https://en.wikipedia.org/wiki/Marchantiophyta
