Japanese beetles have quickly become one of the most detested insects of all time. They are indiscriminate and feed on a multitude of vegetables, ornamentals, trees, and plants. A lot of research is being conducted to combat these gregarious feeding insects. There are options for control that depend on the plant being attacked, the amount of infestation and your level of time. Note there are many websites that have the answer/product/cure/trap for Japanese beetles. When researching online, find a trusted source, such as .edu or .gov or .org, that has actual research and not just anecdotal evidence. Here are a couple of sources I have found to be updated on a timely basis and filled with fact-based information.
https://hnr.k-state.edu/extension/info-center/common-pest-problems/common-pest-problem-new/Japanese%20Beetles.pdf
https://extension.colostate.edu/topic-areas/insects/japanese-beetle-5-601/
http://www.missouribotanicalgarden.org/gardens-gardening/your-garden/help-for-the-home-gardener/advice-tips-resources/pests-and-problems/insects/beetles/japanese-beetle.aspx
https://hnr.k-state.edu/extension/info-center/common-pest-problems/common-pest-problem-new/Japanese%20Beetles.pdf
https://extension.colostate.edu/topic-areas/insects/japanese-beetle-5-601/
http://www.missouribotanicalgarden.org/gardens-gardening/your-garden/help-for-the-home-gardener/advice-tips-resources/pests-and-problems/insects/beetles/japanese-beetle.aspx