Thank you for contacting Ask Extension. Looking at the pictures, it appears that there are other issues along with what is eating your highbush cranberry.

First off, it would be beneficial if you removed 3-4 feet of sod out away from the tree, all around, and mulch with 3-4 inches of mulch. Do not pile the mulch up around the tree, but leave about 2-3 inches from the trunk open. The grasses may be taking up water and nutrients before it can get to the trees’ roots. You need to make sure that the tree is getting at a minimum of 1 inch of water/week if it does not rain. It is a young tree and does not have the root system that an older tree might have.

The tree in the picture has some damage at the base of the tree. It appears to be either tree rubbing by deer or a small animal has chewed the bark around the tree and opened up the cambium layer to insects and diseases. You can trim the bark back to the tree. Do not put anything over this area. This is why it is beneficial to remove the grasses and weeds back from the plant, so that rodents do not have immediate access to the trunk, especially during the winter months.

The insect that might be chewing the leaves is probably the Viburnum leaf beetle (VLB). The best option is to look for the insect and eggs on the underside of the leaves, and kill them. At this point, to spray anything will not be beneficial because chemical control options only work on the larva, that are active and moving only in June to early July. Some insecticides are registered for use against VLB and are generally most effective if applied when larva are active. Spinosad and insecticidal soap are slightly friendlier options in terms of protecting beneficial insects, but they must come in direct contact with larva to be effective.

If you keep your shrubs healthy, well watered, and mulched they should be able to survive.

Here are some publications for your reference:

https://apps.extension.umn.edu/garden/diagnose/plant/deciduous/viburnum/barksmallbrancheschewed.html

https://mortonarb.org/plant-and-protect/trees-and-plants/american-cranberry-bush/

https://extension.unh.edu/blog/2019/06/what-eating-leaves-my-viburnum