Is it?

On a tree? I've only ever seen lichen on rocks.

Is this not lichen then?

https://www.independenttree.com/is-lich ... s-harmful/

I defer to the evidence. As I live in a desert with lots of rocks and few trees, I apparently don't recognize lichen on organic material.

Like on the trees in my yard.

Standing and fallen.

So, to the op: yes or no?

Tough to tell from the photo, but probably.

I've been cleaning up the brush and trees today.

Looks like lichen to me. I got some here I'll let go, cheap.

Since a rolling stone gathers no moss, if you rolled the brush and trees....

My moss is not for sale. I love my moss. It covers a lot of the eastern ground area of the back yard, making winding sylvan trails through the remaining trees southward to the overgrown azalea wall at the southern edge of the estate. Lots of work still to do there, and in the blueberry bushes, and the flower patches around the burial site of our late Lab. Much work ahead.

Moss is good.

Yes, lichen grows on trees.

https://www.google.com/search?q=lichen+ ... e&ie=UTF-8