Mrs. Irish found these on the back of some azaleas we planted about a year ago.

I think they are "tar spots" due to Azalea lace bugs.

Is it or the bugs harmful to the Azaleas? And if so what can I do about it?

Disclaimer: Mrs. Irish (Aka: Granola Granny) ain't going to want to use any pesticides.

They basically use a straw and suck out the chlorophyll out of the plants cells, causing bleached out spots. I think most azaleas will have them and they do alright. I’d imagine can lead to added stress and disease on the plant. I noticed it on mine and got to researching is the only reason I know about it. Haven’t treated them, and they seem okay. Neem oil or pyrethrum are two “organic” ways of control. Proper fertilization and care can help reduce the damage as they seem to prefer already stressed plants. Pretty much my entire yard is leached out sandy crap soil under oak trees which is probably why I have them so bad.