Thank you for your question for Extension Master Gardeners. Unfortunately, now is the peak time for Japanese beetles. They can be relentless in gardens and trees and are difficult to control. When they are in a garden, we recommend taking a jar or soapy water and remove them by hand, so if you can reach them, try this technique. When the beetles are feeding they are sending out signals to others to come join them. Most of the time they will not totally defoliate a tree and the tree will recover. Here is an article from Extension:

 Managing Japanese beetle feeding | UMN Extension

Neem oil is a good preventative but may take some time to react as the beetle ingests the oil. Here is an Extension article that talks about insecticides you might want to consider:

Japanese beetles in yards and gardens | UMN Extension

You may want to consult a certified arborist if you feel you need to. Here is a link to find a certified arborist in your area:

How to hire a tree care professional | UMN Extension