A commercial grower 'gave' me about 100 azaleas that have been through Katrina and an 8-inch snow in the past five years. He was planning to destroy them. I have planted them and have kept them alive this entire very dry summer; however, most all are covered with lichen on their bark. I tried a solution of copper sulfate once but may not have had the solution strong enough. Now it looks like there is something attacking the leaves. They are bleaching out and have lots of white on them. I can see very small black things on the bottom of the leaves, but not all bleached leaves have them.
Treatment of Lichen on Azaleas
Certified GKH Gardening Expert
The pest is azalea lace bugs. The lichen tends to grow on stressed plants and the lace bug is causing the stress. If you get rid of the lace bug, that should make it easier to treat the lichen. These articles will help you: