We'd need to see pictures to be really helpful. Could be something as benign as lichen.

If you can't do the images, then try to come up with a better description.

lichen pix at the link below

it was the first thing i thought of...

i have heard of peeps who pay to have it applied to there trees ... apparently peeps with too much money .. lol

ken

Here is a link that might be useful: link

Have it applied? What do you mean? To kill them?

it can give an ancient look to bonsai ...

you seem intent on removing a bonus that mother nature has given to you ...

if in fact they are lichen ... a pic would sure help.. if the google pix werent good enough for you to recognize it ...

its natural ... it in no way harms the tree .. its a BONUS ....

ken

The lower branches are probably dying because of the lack of light, not the green spots of lichen or moss.

Not to confuse the issue, but here's an extreme example of lichens growing on a Acer macrophyllum. I leaned the branch up against a Western Hemlock. The maple tree was very healthy before getting cut down for firewood.
{{gwi:346640}}

Are you sure it's not pollen?