You have answered your question. Determine the identity and benefit (or not) of the insect, and then pursue the path less traveled.

I suspect that you are observing several things:

• an insect's larval stage that prefers this species
• the variation in resistance to or preference for insect herbivory across a species in named selections

If you were to look it up (Dirr, Ladman, perhaps Bailey or Krussmann) you will find that these selections were made from quite different places. It doesn't surprise me that a native insect in northern WI might not be found in northeast North America.

Find out what predator favors your leafroller, and let the games begin...

Dang, that sounds like homework. ;)

Viburnums seem to have a full host of leaf predators, at least mine do.

What struck me as I unfurled the leaves and found the larva wrapped so neatly was how do they do it? Time lapse photography of this would be interesting. I’m guessing it doesn’t take them very long.

Viburnum Valley, after reading your post, I started thinking about how I could attract a natural predator. This would be a noble effort, but could also be frustrating and ultimately ineffective. The other two look perfect and they will hopefully cross pollinate for maximum fruit production. I guess what I’m trying to say is Wentworth will be exiting the garden.

Here’s Bailey’s Compact and Red Wing.