The larvae may have all crawled down into the soil to pupate. If so, the adults will emerge in mid-summer and start chewing the leaves again. I did notice something else though that makes me think of a different outcome. One day as I stood looking at the highbush cranberry, two tufted titmice called from the shrub. I had not noticed them hanging out there before. I wonder if these birds ate all the larvae. Wouldn't that be nice. Coincidentally, or not, I saw a titmouse in the highbush cranberry in the backyard. And that bush was only minimally defoliated.
Now, two weeks later the highbush cranberry is recovering. New leaves are emerging. If I see no new viburnum leaf beetles this summer, I will be convinced that the tufted titmouse saved the bush.
fresh leaves of the highbush cranberry
emerging after defoliation by the viburnum leaf beetle