Lilac Shelf Fungus

Suddenly this fungus has appeared along the lower branches of fine old lilac. I assume it is about fifty years or older. The flowers are deep purple and exceptionally fragrant. It is my very best lilac.
This past spring I planned to cut down the few old branches that produce almost no leaves or flowers. Yet the birds like to sit in it to crack their sunflower seeds.
Now I see the old branches must be very dead for shelf fungus to be growing on them. It rather suddenly appeared this autumn. We have had a very wet one.  The recent snow has all but melted, with rain all day today.
The new purple lilac bush is sending out these thin branches that will be bloomers in a few years, I guess.
Maybe I will cut down the original branches next spring.