I have a Blue Muffin Viburnum just outside my office window and noticed that it was being defoliated and the leaves were almost bare, so I did a little research.
Larva of viburnum leaf beetle. Once I learned about this I went out and found many larvae on the underside of the leaves of the viburnum. Apparently these beetles have moved into the Chicago area and viburnum dentatum cultivars, of which I have four bushes, are highly susceptible. One can prune the bushes in the winter when you can see where the beetles have laid eggs on the twigs. Otherwise, what I did was to brush the larvae into a bucket of soapy water. There were maybe 30 that I brushed in the bucket, but I am sure I missed many. Currently this bush is in bloom and was only defoliated on the back branches.
Another Arrowwood viburnum dentatum I have is a cultivar ‘raspberry tart.’ This one was almost completely defoliated before I noticed it. I hope it survives until next year, but it may have the same problem again…. One result of all these larvae is that I think they attracted additional birds this year.
This year is the first year I have seen catbirds in our yard and they seem to be hanging around. This catbird was finding larvae in the viburnum leaves.
This catbird spent some time poking around the strawberries, too.
So I am not sure of the future solution for the viburnum. I will see if we can get ahead of these beetles, but if not we may need to plant other cultivars of viburnum that are not as susceptible to them.