The Blob is on My Plum Tree

[Bert Byfield]

This is a link to some pictures of "The Blob" (dark brown stuff wrapped around the branches, about a hundred of them, three or four inches long) which has attached itself all over my Italian Prune tree in upstate New York. Does anyone know what this is and what I should do to it?

[Boron Elgar]

Looks like black knot, a fungus.

[Amos Nomore]