That sounds like it might be the tent caterpillar. Is there a caterpillar hiding in amongst the webby material?

Here is a link that might be useful: Tent or Web-making caterpillars

I can't find a caterpillar, no, although there must be something making the web! The web is mostly limited to the flower blossoms.

So, further investigation indicates it might be the winter moth here, not the tent caterpillar.

Damn things!

Here is a link that might be useful: Winter moth topic in this forum

Oh, wait. You said it wasn't that. Hrm. then I don't know!

I too have something eating my dentatums but not my burkwoodii. When I turned the leaves over, I saw a couple of tiny green worms/caterpillers. Do you know what these are? The blue muffin and chicago lustre haven't given any flowers yet - maybe because of the problem with the folliage. All the other plants look healthy and have already flowered. Any help would be appreciated.

Peony - I have the same thing, and only on my V. dentatums also. They are tiny and almost look like maggots. Tthey are eating small holes in the leaves and sometimes webbing leaves together. I've had them for a couple of years.

This page has some pictures, and I'm guessing that what we have is Viburnum Leaf Beetles. I think I will be removing this plant and burning the leaves.

oops, forgot to attach the link

Look at the photos of the larvae - looks just like mine.

Here is a link that might be useful: Viburnum leaf beetles

Thank you nhbabs for the link for Virburnum Leaf Beetles. This spring, my Arrowwood viburnums were loaded with caterpillars exactly like the ones pictured on this site.

At first I sprayed with insecticidal soap, but later I decided to try BT. The caterpillars really did a number on my bushes and all the leaves are practically skeletonized. Thankfully the BT worked, and I haven't seen a caterpillar since.

I'm just hoping that the bush will recover sufficiently and I plan to prune it heavily as they have suggested.

Next year I'll start spraying early with BT to get a head start before they do too much damage.

So after looking at this I check out MY Viburnum shrubs... IT's been 4 years and I have yet to have it flower... well it TRIED to flower... and something nibbled JUST the flower it's self. The panicale is intact... just no petals....
Is that the Winter moth or the beetle ?

Viburnam beetle causes these holes. They can strip the whole bush. The RHS called it the No. 1 pest in 2010. Spray with pyrethrum April to September. See http://www.gardenersworld.com/how-to/problems/ornamental-trees/viburnum-beetle/455.html. Gardener's World.com