Ends of branches die when rhododendron or azalea borer larvae tunnel in a stem. This affects the portions of the plant away from the roots from where the borer larvae is in the stem. Borers have done their damage when you see the wilting and usually it is best to cut off the affected region. The requires removing the damaged branch from the hole where the eggs were laid at the base of the dying branch to remove any larvae before they become adults and infect more plants. The parts that are cut off should be destroyed to kill the larvae that are in them. Borers are prevented by following a spray schedule (timing is very critical) for borers with chlorpyrifos or lindane. Your county agent can help you with this information.

Buds and twigs becoming covered with silver-gray scales is caused by the fungus Briosia and is easy to control with fungicide sprays and proper sanitation by removing and disposing of all dead material. Check with your county extension agent.

Here is a link that might be useful: Common Problems & Their Solutions

Really helpful website. Thank you.