Lichen

Help.... does any one know why the lovely Azaleas are covered in the most horrible scab like growths that have been identified as lichen,what is the cause and the remedy..they are established plants and appear quite healthy. :(

 

Lichen tends to grow on things that remain damp for a certain amount of the year, although they can stand complete drying out for long periods.
Seem to remember reading something about them only growing in areas where there is not much pollution. They wont harm the plants, they are not parasitic, but you could rub them off if you dont like them.