Do you think it might have come from the nursery maybe their viburnum's aren't as hardy to disease and insects as the one you dug up from the wild? Just a thought since I buy alot of plants from a native plant nursery in my area and I notice alot of aphids on their plants. Sarah

Any two individuals of any species will vary on an infinite number of traits. That's the basis of natural selection and evolution. That's why a few individuals will always survive any infestation. There are hemlocks that don't succumb to wooly adelgids, and there are HIV-infected people who don't get AIDS. Have you ever been the only one in your family to get a cold? Everyone else but you was immune. Same with your plants.

Also, I believe that viburnums are self-fertile, so there's no way of knowing if your two are cross-pollinating or not. They probably are, but you have no way of knowing unless you analyze the genes in the seeds they produce.

That is a very interesting thought, thanks Elaine.
About the cross-polination, very empirically, I can assure you that the "moment" I planted the 2nd specimen, fruit production from the 1st one increased at least hundredfold!

I believe it's true with Japanese Beetles that the beetles attract more beetles with pheromones so with my Crape Myrtles that are exact clones of each other, I might have dozens of Japanese Beetles on one but none on the other. It seems to be only temporary though. They eventually find both. Perhaps something similar is happening with your viburnum beetles. And of course where the eggs are laid makes a difference.

Here is a link that might be useful: viburnum leaf beetle life cycle

Thanks immensely, Christie!

I have also noticed this "phenomenon" with aphids in my garden---last year when I started butterflyweed (Asclepias tuberosa) from purchased seed, the aphids attacked the small seedlings. They also attacked my swamp milkweed that I got via a nursery.
I've never seen aphids on butterflyweed/milkweed in the wild. Luckily this year, my plants grew right up and are double the size that they were when they got attacked last year.