How can I rid my Cherry tree of Japanese beetles?
If the tree has an active infestation you will need to spray with a potent bio-pesticide (organic program compatible but more expensive) like pyrethrum (pyrethrins) as a contact spray for knock down.
Or use a chemical insecticide like permethrin.
(very effective and less expensive)
Follow label rates for mixing and read precautions for personal and environmental protection. (Both are low toxicity for mammals but highly toxic to fish and honey bees.)
After you get the active infestion under control, you can spray preventively with 70% neem oil on a repeated basis during the growing season.