Question
Could this cause my bush to die?  

Answer
Hi Carol,                                                             How r u! Lichen is not the problem people think it is.It is a harmless fungus.It is however ugly to look at on azaleas.U can treat it with a fungicide but i would leave be.If your plants r not looking there best something else is the problem.If u ever have any more questions just ask!!!!!!!!!!!!!!!!!