Those white things are the critters. I see similar photos for ones that are not supposed to occur on this type of viburnum, and maybe don't occur locally, so I will leave the ID and a link to what to do about them to someone else.
They look like Cottony Camellia Scale, which affects many species besides Camellia, described in many websites, including this one: https://pnwhandbooks.org/insect/hor...ants/camellia-camellia-cottony-camellia-scale. That website doesn't mention Viburnum, but other websites do. I get these pests on hardy kiwi vines and Pieris japonica.
How do you control it? It only affects the underside of the lower branches (it is a viburnum bodnantense). The tree is otherwise flourishing, probably 15-20 ft tall. Could the soil beneath be an issue? It is right next to a big old rhododendron which isn’t affected (but has other issues…) Thanks
If the infestation is somewhat restricted to the lower branches and leaves you could remove the infested leaves and dispose of them and then rub the branches where there is scale with rubbing alcohol to kill off the remaining insects. If the infestation is small relative to the size of the tree the percentage of leaves removed shouldn't affect the plant long term as there would still be enough foliage to allow photosynthesis to continue. I think the key is to get at it before it might spread to the whole tree which can become a much more difficult problem to treat. Info in the link below including an organic spray solution. scale-insects
Since this is a non-edible plant, there are many options for chemical control; but I've only investigated horticultural oil. Though I haven't tried it, I've read that it can be applied during the dormant season and then again around late May and early June.
