Identifying a shrub with unusual “many shoots” growth behavior

While recently hiking in the southern mountains of New Hampshire, we came across a plant, and some of them were exhibiting what we interpreted to be a disease, or least unusual growth. On some of the nodes, there were a large number of extra stalks:

On each plant, the number and locations of these things varied, and not all of them had it. And we first assumed it was some ivy, or parasite, or separate plant, but it seemed pretty clear to us that it was coming right from the same branch.

We soon saw there were dead versions of this plant, and all of them had this "extra shoot" variation:

So we reasoned that no matter what this thing was -- natural variation or some kind of disease -- it was killing the plants.

Google image search was no help. It possibly identified the plant as a "viburnum", but was unable to help with the growth.

Anyone know what plant this is, or what this growth behavior is the result of?

Possibly an example of a "Witch's Broom."

Witch's Broom is a deformity in plants (typically woody species) which typically causes dense patches of stems/shoots to grow from a single point on the plant. The name comes from the broom-like appearance of the stems.1

Witch's broom may be caused by many different types of organisms, including fungi, oomycetes, insects, mistletoe, dwarf mistletoes, mites, nematodes, phytoplasmas, or viruses.2

Sources: 1. Wikipedia 2. Book of the British Countryside. Pub. London : Drive Publications, (1973). p. 519 Image1. Image2. Iowa state University

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